Answer:
19
Step-by-step explanation:
The triangle is an isosceles and so angle SRT and angle STR are equal
also:
Angle SRT and angle STU are supplementary so their sum is equal to 180
7x + 2x + 9 = 180 add like terms
9x + 9 = 180 subtract 9 from both sides
9x = 171 divide both sides by 9
x = 19
