9x-3x-5-3=2x-12
12x -8 =2x-12
-2x. -2x
10x. -8. =-12
+8. +8
10x. = -4
X = -0.4
After 2 weeks:
15+3(2)=15+6= $21
After 5 weeks:
15+3(5)=15+15= $30
After 10 weeks:
15+3(10)=15+30= $45
Hope this helps
35 which is slope which in turn represents the speed.