456+x=956. 1,501+x+4,657. 89+x=95.

Answer 1

Oh and

78-x=42. 875-x=100. 678-x=545

Answer 2

These are all done in exactly the same way: get x all alone
456+x=956 -- subtract 456 from both sides
x = 500

78-x=42 -- subtract 78 from both sides; that gives you
-x = -36 -- so now multiply both sides by -1 to get
x = 36

Answer 3

Oh okay thank you.