Answer:
x = 19
Step-by-step explanation:
Let's convert the given statements into algebraic expressions.
R is five more than twice x:
R = 2x + 5
S is one more than x:
S = x + 1
T is sixteen less than seven times x:
T = 7x - 16
Also, we know, the sum of 3 angles in a triangle is ALWAYS EQUAL to 180 degrees. Thus we can write:
R + S + T = 180
Substituting the expressions, we have:
2x + 5 + x + 1 + 7x - 16 = 180
Now we do algebra and simply solve for x. Shown below:

Hence, x = 19