Answer:
The measure of Angle S is 75 (degrees).
Explanation:
Key skills needed to solve this are: Sums of a triangle, one variable equation, operations
1) All the angles in a triangle add up to equal 180 degrees.
2) We can use this to say that Angle S + Angle R + Angle T is 180 degrees.
3) Subsitute in the expression for each angle: 7x+40+8x+25+5x+15 = 180
4) Combine like terms
7x + 8x + 5x is 20x & 40 + 25 + 15 is 80
This means that 20x + 80 = 180
5) Move 80 to the right side: 20x = 100
6) Divide by 20 andbget x equal to 5
7) To find Angle S, you need to plug in 5 into the expression.
7x + 40 = 7(5) + 40 = 35 + 40 = 75 degrees
The measure of Angle S is 75