Simplify. Note the equal sign. What you do to one side, you do to the other. Follow PEMDAS.
Isolate the x.
First, distribute 6 to all terms within the parenthesis
6(-3) = -18
6(4x) = 24x
7x - 18 + 24x = 199
Simplify. Combine like terms
31x - 18 = 199
Isolate the x. Add 18 to both sides
31x - 18 (+18) = 199 (+18)
31x = 199 + 18
31x = 217
Isolate the x. Divide 31 from both sides
31x/31 = 217/31
x = 217/31
x = 7
7 is your answer for x
hope this helps