It's a linear function. We need only two points to the plotting of the graph.

Simply 4/6 to its equivalent fraction of 2/3
Is 1/3 of a cup enough for the 2/3 a cup needed? No. So he doesn't have enough
3.125 as a fraction is 25/8
4x-7x= 13
⇒ -3x= 13
⇒ x= 13/(-3)
⇒ x= -13/3
The final answer is x= -13/3~