Brainleist answer will be given : )

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 :)

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