Question 390419
x=-3s,x=10-4s

Replace all occurrences of x with the solution found by solving the last equation for x.  In this case, the value substituted is -3s.
x=-3s_(-3s)=-4s+10

Remove the parentheses around the expression -3s.
x=-3s_-3s=-4s+10

Since -4s contains the variable to solve for, move it to the left-hand side of the equation by adding 4s to both sides.
x=-3s_-3s+4s=10

Since -3s and 4s are like terms, subtract 4s from -3s to get s.
x=-3s_s=10

Replace all occurrences of s with the solution found by solving the last equation for s.  In this case, the value substituted is 10.
x=-3(10)_s=10

Multiply -3 by each term inside the parentheses.
x=-30_s=10

This is the solution to the system of equations.
x=-30_s=10