Question

Shayne wants to earn money to attend a basketball camp. For her 8th-grade graduation, her grandmother gave her part of the money she needs. Every month since then, Shayne has been saving the same amount from her babysitting jobs. After 3 months she had $155, and after 7 months she had $295. Which equation describes the relationship between x, the number of months Shayne has been saving, and y, the amount she has saved?

Answer 1

y = m x + b

295 = m * 7 + b
155 = m * 3 + b
------------------subtract
140 = 4 m
m = 35
so
y = 35 x + b
now put a point in
155 = 35(3) + b
b = 155 - 105
b = 50
so
y = 35 x + 50