you can subtract 4.2 from both sides of the equation.
16=x+4.2
(16)-4.2=(x+4.2)-4.2
11.8=x+4.2-4.2
11.8=x
5+x=42. 42-5=37 x=37
-55
The answer is 7
15
2x - 13x + 42 = x +ax + b a + b = 2(x - 6.5x + 21) = 34 = a + b
42 72
x = 14
x=-1.6
If: x+16 = 9x then x = 2
x=6
16
x = -14