Mmmmmmm I would say the equation is y = 52x + 12 because 52 dollars per week is the slope, 12 dollars is the extra so it will be b in the equation y = mx + b. So you will end up with y = 52x +12. :)
Since the denominator has to be 100 and 9/10, 0.90, and 90% are all equal the you would just need to make the 9 into a 90. Therefore, yout answer will be 90/100.