Isolate the x. Note the equal sign. What you do to one side you do to the other.
Subtract 2y from both sides
2x + 2y (-2y) = 10 (-2y)
2x = 10 - 2y
Isolate the x, divide 2 from both sides and from all terms.
(2x)/2 = (10 - 2y)/2
x = 5 - y
Place the variable in the front
x = -y + 5
x = -y + 5 is your answer
hope this helps