Uhhhhh yes.?
love that for u
Since y=3x+15
sub 3x+15 for y in other equation
2x+3(3x+15)=1
2x+9x+45=1
minus 45
11x=-44
divide 11
x=-4
sub
y=3x+15
y=3(-4)+15
y=-12+15
y=3
(-4,3)
The vertex is halfway between 700 and 800, and the x value of the vertex is right over the 10. So since the x value represents dollars, the maximum (vertex) is 10$ each for 750$