Question

determine the value of a so that the graph of the equation passes through the given point

Answer 1

3x+ay=15 (-2,3)

Answer 2

That's an equation of a line.

So rearrange the equation

ay=15-3x
y=15/a -(3x)/a
y=(15-3x)/a

Substitute the point (-2,3)

3=(15-(3)(-2))/a

simplify

3=21/a

Solve for a

21/3=a
7=a