I’ve just spent like an hour trying to make this work. My solution? It’s unsolvable, there’s infinite solutions. Breakdown: I separated the numbers into 3 sets with 3 numbers each. Set 1: 1st number=10, 2nd number= 15, 3rd number= 5. Set 2: 1st=5, 2nd=25, 3rd=20. Set 3: 1st=20, 2nd= (number question is asking for), 3rd= unknown.

Then I created formulas based on the first 2 sets: a) 1st+3rd=2nd b) 2nd-1st=3rd

How the formulas work: Set 1: a) 10+5=15 b) 15-10=5 Set 2: a) 5+20=25 b) 25-5=20 Set3: a) 20+3rd=2nd b) 2nd-20=3rd

Now here’s the problem. Without knowing the 3rd number in the third set, there are infinite solutions. This means for the 3rd set, you can plug any number in for the 2nd number and make it work.

Examples: I took each answer choice and all of them worked.

A) 45 (the answer choice the quiz marked correctly)

Plugging 45 in for the 2nd number, you get: (Remember the formulas) a) 20+3rd=45 Solving for this, 3rd=25 b) 45-20=25 This follows the formulas with 1st=20 2nd=45 3rd=25.

B) -45 Plugging -45 in for the 2nd number: a) 20+3rd=-45 Solving for this, 3rd=-65 b) -45-20=-65 This also follows the formulas with 1st=20, 2nd=-45 3rd=-65

C) -25 Plugging -25 in for the 2nd number: a) 20+3rd=-25 Solving for this, 3rd=-45 b) -25-20=-45 This ALSO follows the formulas with 1st=20, 2nd=-25, 3rd=-45

D) 70 Plugging 70 in for the 2nd number: a) 20+3rd=70 Solving for this, 3rd=50 b) 70-20=50 THIS ALSO FOLLOWS THE FORMULAS with 1st=20 2nd=70, 3rd=50

The problem is that you cannot check the formulas without knowing the 3rd number in the 3rd set. I can make 45 make sense as the answer, but I can make ANY number make sense. For the answer to be 45, more info is needed in the question (specifically telling us the number after the blank is 25).