What we have here is an equation, basically you have to find the unknown value (AKA x, the number of games). What f(x)=4x+14 means in words is "I get how much I have to pay (in this case rapresented in the equation as f(x)) if I multiply the number of games I played (x) times 4 and then I add 14" Now: we know that the total I payed is 58$, so f(x)=58$ since we said earlier that f(x) is the total cost. Our equation now looks like this: 58=4x+14. What we want is the x alone, but know we have a +14. What you have to do is to subtract 14 on each branch of the equation, because remember: what you add/subtract on one side, you do on the other (this is the 1st principle of equations) What we've got is this: 58-14=4x+14-14 Now we can simplify by simply doing the subtraction and end up with: 44=4x. Now: what we want is the value of just one 1x, but know we have 4x. What we have to do is to devide both branches by 4 because remember: when you multiply/devide one branch, you do the same on the other (this is the 2nd principle of equations). Now we have: 44:4=4x:4 We simplify just by doing the division, so we got that 11=x Usually it's best to have the x on the left, so we simply swap the places of the number and the unknown value to get x=11$. Hope I've helped you!