Answer:
substitute the 'x' with any number
Step-by-step explanation:
an example of this could be, if you need to find
y=2x+6
you would need to find what y is
in order to do that, subsitute x for any number, example, 2, and work out the equation. 2x means 2 times 2 (x is substituted by 2). that is 4 and +6 is 10. this means y would be 10. this is how substitution happens:)