Respuesta :

x + 65 = 120
    -65      -65

x = 55
To solve for x we will use the INVERSE OPERATION of addition which is subtraction. Lets do it:-

x + 65= 120
x = ?
120 - 65 = x
120 - 65 = 55
x = 55

CHECK OUR WORK:-

x + 65 = 120
x = 55
55 + 65 = ?
55 + 65 = 120
We were RIGHT!!!!

So, x = 55.

Hope I helped ya!! xD