Short Answer x = 66
Remark
2x is the supplement of a 48 degree angle.
Supplementary angles add up to 180°
Equation
48 + x + x = 180 Collect like terms
Solution
48 + 2x = 180 Subtract 48 from both sides.
2x = 180 - 48
2x = 132 Divide by 2
x = 66 <<<<<<< Answer