Answer
$M=20x +7.5 y$
$x=15; y=0$
$x=12; y=8$
$x=9; y=16$
Work Step by Step
Here, we have $M=20x +7.5 y$
When $M=300$
$20x +7.5 y=300$
Now $[20x +7.5 y=300] \times 2$
We have $40 x+15 y=600$
This gives: $8x+3y=120$ or, $x=\dfrac{120-3y}{8}$
When $y=0$ then $x=\dfrac{120-3(0)}{8}=15$
When $y=8$ then $x=\dfrac{120-3(8)}{8}=12$
When $y=16$ then $x=\dfrac{120-3(16)}{8}=9$
Hence, $M=20x +7.5 y$
$x=15; y=0$
$x=12; y=8$
$x=9; y=16$
