∠1 and ∠2 are supplementary angles, and so they will equal 180°
note that:
m∠1=4x+3
m∠2=3x−5
Plug in the corresponding expression for the angle
(4x + 3) + (3x - 5) = 180
Simplify. Combine like terms
7x - 2 = 180
Isolate the x. Note the equal sign. What you do to one side you do to the other.
Add 2 to both sides
7x - 2 (+2) = 180 (+2)
7x = 182
Divide 7 from both sides
7x/7 = 182/7
x = 182/7
x = 26
26 is your answer for x.
hope this helps