m∠3 = 180 - m∠8 = 180 - 123 = 57
m∠1 = m∠3 = 57°
Answer:
This question is incomplete. What exactly are we doing to the equation
PS; You can answer in the comment section. I'd help out there
Hi there!

Begin by distributing the 5:
5(2x) + 5(-12) = -90
Simplify:
10x - 60 = -90
Add 60 to both sides:
10x = -90 + 60
10x = -30
Divide both sides by 10:
x = -3
Answer:2x+30 =90
If the angle is 90° altogether
60=A 30=30
Step-by-step explanation:
2x+30 =90
-30 -30
2x=60
÷2. ÷2
x=30
2*30=60
60+30=90
60=A B=30
Mean=total/the number of values =>total=mean*the number of values
the total of the first set of 8 numbers is : total=8*8=64
the total of the second set of 12 numbers is: 12m
the total of the 20 numbers is: 64+12m
the mean of the 20 number is: (64+12m)/20=5
solve for m: 64+12m=100
12m=36
m=3