Question

If y = 8 when x = 4, find y when x = 5. how do ii solve this

Answer 1

there is no good solution for this unless you have a general form your answer has to be in terms of.
for example, the equation governing this system could be y=2x, which would give you y=8 when x=4, or the equation could be y=x+4, y=3x-4, or any of an infinite set of equations.
if you want a good answer for this, you need to tell us what the general form you are looking for is