Question

if the point (3, 5) lies on the graph of the equation ax+y=20​

Answer 1

a×3+5=20

3a+5=20

3a=20-5

3a=15

a=15/3

a=5

Answer 2

$\mathfrak{Hola!}$

If the point (3,5) lies on the graph ax+y = 20

Then, x = 3 and y= 5

Substuting the values in the equation  

ax + y = 20     , we get

3(a) + 5 = 20

3a = 20-5

3a = 15

a = 5

$\boxed{a=5}$