To find the first blank, just replace x in the equation with 12 and solve. a(12) = 50 - 1.25(12) = your answer for blank 1
For blank 2: because x represents the number of apps on her phone, and x is given 12 for this problem, she bought 12 apps.
For blank 3: You would mention how many apps she got twice, so not the first option or the third option. It should be the answer from the first blank because the equation represents how much money is in her account.
