X=12.5
If the perimeter is 90
90=3x+3x+15
Combine like terms
90=6x+15
Subtracts 15 from both sides
75=6x
Divide by six to get x by itself
12.5=x
Does this help?
Step-by-step explanation:

The first missing number in the sequence is 35, and the last missing number is 77.
<h3>Next number of the given sequence</h3>
The two missing numbers in the given sequence is calculated as follows;
= ? 49 63 ?
The given sequence is factor 7 which increases by 2
= 7 x 5 7 x 7 7 x 9 7 x 11
= 35 49 63 77
Thus, the first missing number in the sequence is 35, and the last missing number is 77.
Learn more about sequence here: brainly.com/question/6561461
#SPJ1
There are 12 boys 21/7=3 so 4(3)= 12
You are welcome
Answer:
x = 36
Step-by-step explanation:
<em>A triangle has 180°</em>.
That <em>third angle is 360 - 8x</em>.
So the equation is: <em>180 = 2x + x + 360 - 8x</em>.
Simplify: 180 = -5x + 360
Add/Subtract: 5x = 180
Divide: x = 36.