Question

How do use u substitution?

Answer 1

The substitution method is used to find the values. Simply replace the equations into another, and solve for the 2 values. 

Answer 2

In the form of algebra substitution is the method used in simultaneous equations.
E.g y=2x+5 and y=5x-1
Solve for x and y
Since we know two examples of what y is, we can substitute one y in replacement of the other to get.
2x+5=5x-1 then we solve for x to get:
x = 2 sub this back in to get y = 2(2) +5
y = 9