Answer:
x =25
Explanation:
This is an isosceles triangle because RS = ST
that means <r = <STR
4x-70 = STR
<STR + <STU = 180 straight line
subtract < STU from each side
<STR = 180 -<STU
we know angle stu = 6x
<STR = 180 -6x
we can substitute this into 4x-70 = STR
4x-70 = 180 -6x
add 6x to each side
4x+6x -70 = 180 -6x+6x
10x -70 = 180
add 70 to each side
10x-70+70 = 180+70
10x=250
divide by 10
10x/10 = 250/10
x =25