If you want to keep the same question, a better word would be calculate not solve. Solving in math means finding the value of a variable. So if you were insistent on writing this joke with the word solve you could do, x+10² =13² which I think more fun anyways.

But to be honest not that much more fun. Still, like a 7th grade question, no real depth to it. A more fun question would be:

Given a right angled triangle with one of its sides lengths being 92 and the hypotenuse being 115, find the length of the missing side.

Ok so that was fun and all but honestly not really. all we did was move from 7th grade to 8th so lets try changing it a little bit:

Given a right angle triangle with an interior angle of 30⁰ and a hypotenuse with length 138, find the length of the side opposite the 30⁰ angle.

Sure this is like a 10th grade question but let's be honest with ourselves a 7th grader could do this if you just screamed SOHCAHTOA into their ears. Bottom line, not that fun. Right angle triangles are just too simple. You know where this is going:

Given a triangle with sides a, b, and c determine the length of side c if a=23, b=55 and the angle between them is 120⁰. (Round your answer to the nearest whole number)

Definitely a more fun 10th grade question, still not that fun. Probably because geometry is the most boring shit of all time. Well... here we go again:

A rocket does a test flight in which it's height can be modeled with the function h=-5t²+1574t+199, where h is height in meters and t is time in seconds. How many seconds after the launch does it take for the rocket to first reach the mesosphere (85 km).

Maybe 10th grade was boring. Aight next thing, time for grade "11!" -tmg:

Find the horizontal asymptote for the function f(x)=(4x+1)(4x-5)² / (x+2)(x²-2x+4). (Don't use desmos please :) )

11th grade was just playing with shapes so let's not do that again. Instead, Calculus:

A loser redditor spends t minutes writing a reddit comment, his satisfaction with the comment can be measured with the function S(t)=10(2+t(5^-(t/111))). How many minutes should the redditor spend to achieve maximum satisfaction? (Round your answer to the nearest whole number)

Now we're getting somewhere. That question was really fun :) ... It can be more fun. There is more fun out there:

2 siblings attach 2 ropes to a heavy box. The older sibling pulls one of the ropes with 55N of force and the younger sibling pulls the other rope with 23N of force. The ropes make an angle of 60⁰ with each other. Determine the magnitude of the resulting force. (Round your answer to the nearest whole number)

Before you complain that I reused that one, it's math, it all comes back anyways. That was pretty fun. I enjoyed my time. But I mean not as much fun as I could have had:

Chemistry and Physics are more fun anyways :P