Answer:
For #21, x = 35, y = 85
Explanation:
For these types of problems, you will simply use to facts. The sum of the measure of a line is 180 degrees, and alternate angles of crossing lines are equivalent. With that being said, let's work #21.
We can see that there are two lines, and we are given 2 values to find with 3 possible equations.
[1] ( 2x + 25 ) + y = 180
[2] y + ( 3x - 10 ) = 180
[3] 2x + 25 = 3x - 10
Using any of these equations, we can solve for the variables. Let's use the 1st and 3rd equations to find x and y.
2x + 25 = 3x - 10
2x + -2x + 25 + 10 = 3x + -2x + -10 + 10
35 = x
Now plug in the value of x to find y:
( 2x + 25 ) + y = 180
( 2(35) + 25 ) + y = 180
( 70 + 25 ) + y = 180
95 + y = 180
y = 85
We can check these values by plugging into the 2nd equation
x = 35 ; y = 85
y + ( 3x - 10 ) = 180
(85) + (3(35) - 10) = 180
85 + ( 105 - 10) = 180
85 + 95 = 180
180 = 180
Thus, we have validated our results and found the values of x and y.
Cheers.