∠1 and ∠2 are supplementary. ∠1=124°∠2=(2x+4)° select from the drop down menu to correctly answer the question.

Remark
Supplementary angles add up to 180o. 

Givens
<1 = 124
<2 = 2x + 4

I imagine you are looking for either x or <2. 

Equation
<1 + <2 = 180          Substitute the givens
124 + 2x + 4 = 180  Collect like terms on the left.
128 + 2x = 180         Subtract 128 from both sides
2x = 180 - 128          Collect like terms on the right   
2x = 52                     divide by 2
x = 52/2
x = 26 <<<<<<<<< answer

<1 = 124
<2 = 2x + 4 = 2*26 + 4
<2 = 52 + 4
<2 = 56  <<<<<<<< answer

We need choices if you want an exact answer.

The first option would be correct if it were one half and not one