Answer:
x = 34
∠S = 38
∠T = 111
Explanation:
Angles in a triangle add up to equal 180
If ΔRST is a triangle and ∠R, ∠S and ∠T are angles in that triangle
Then ∠R + ∠S + ∠T = 180
That being said we want to create an equation to solve for x
If angles in a triangle have a SUM of 180
Then, 31 + x + 4 + 3x + 9 = 180
We now solve for x
Step 1 combine like terms
31 + 4 + 9 = 44
x + 3x = 4x
we now have 44 + 4x = 180
step 2 subtract 44 from each side
44 - 44 cancels out
180 - 44 = 136
We now have 136 = 4x
Step 3 divide each side by 4
4x / 4 = x
136 / 4 = 34
We're left with x = 34
Now we want to find the measures of ∠S and ∠T
To do so, we substitute 34 for x in their given expression
∠S = x + 4
* substitute 34 for x *
∠S = 34 + 4
34 + 4 = 38
Thus ∠S = 38°
∠T = 3x + 9
* substitute 34 for x *
∠T = 3 ( 34 ) + 9
34 * 9 - 102
102 + 9 = 111
Thus, ∠T = 111°