The equation for David's graph:
(125-100)/(4-2)
25/2=12.5
y=12.5+75 (75 is where the graph starts)
they have to equal the same so:
12.5x+75=15x+50
Multiply each side by 2:
25x+150=30x+100
-100 from each side:
25x+50=30x
-25x from each side:
50=5x
Divide each side by 5:
10=x
They would have to work 10 hours to earn the same amount of money.
Hope this helps :)
