If you mean 5x+y = 21 and x = 6-2y then x = 4 and y = 1
5x plus 3 does equal 3 plus 5x; commutative law.
-10x + 5x = -5x
2xy
x=6
It is: 5x
5x+5x-10 10x-10 is the only answer you can get from this
10x - 5x + 5x = 10x
-5x^2 - 55x - 120
2x plus 5x simplified is 7x.
5x+2x=7x2x + 5x = 7x
It is an algebraic expression which cannot be evaluated without information about y.
3