Answer:
[tex]\boxed {\boxed {\sf x= 12}}[/tex]
Step-by-step explanation:
We are asked to solve for x. We are given a triangle and all 3 angles are labeled. We know that the sum of the angles in a triangle must be 180 degrees. Therefore, the given angles: 81, 57, and (2x+18) must add to 180. We can set up an equation.
[tex]81+57+ (2x+18)= 180[/tex]
Now we can solve for x. Begin by combing like terms on the left side of the equation. All the constants (terms without a variable) can be added.
[tex](81+57+18)+2x=180[/tex]
[tex]156+2x=180[/tex]
We will solve for x by isolating it. 156 is being added to 2x. The inverse operation of addition is subtraction. Subtract 156 from both sides of the equation.
[tex]156-156+2x=180-156 \\2x=180-156 \\2x= 24[/tex]
x is being multiplied by 2. The inverse operation of multiplication is division. Divide both sides by 2.
[tex]2x/2= 24/2 \\x= 24/2 \\x=12[/tex]
In this triangle, x is equal to 12.
