Remember: PEMDAS - Parentheses, exponents, multiply/divide, add/subtract
Distribute: 9(1+x) = 9+9x
19 - 5x = 9 + 9x
Add 5x to both sides of the equation and subtract 9 from both sides.
19 - 5x + (5x) = 9 + 9x + (5x)
19 - (9) = 9 - (9) + 14x
10 = 14x
Divide both sides by 14 to get the variable on its own.
10/14 = 14x/14
10/14=x
5/7 = x