1. 21=a+a+4+2a-3
4a+1=21
4a=21-1
4a=20
a=20:4=5
2. x+2x+20+7x-10=180
10x+10=180
10x=170
x=170:10=17
3. x+30+2x-60=180
3x-30=180
3x=180+30=210
x=210:3
x=70
4. 2(2x+3+x-2)=44
2(3x+1)=44
3x+1=44:2=22
3x=22-1=21
x=21:3
x=7
5. 48=2(4+x+5)
x+9=48:2=24
x=24-9
x=15
6. 3x+6=5x
6=5x-3x
6=2x
x=6:2
x=3
7. x+10+2x-40+3x-90=180
6x-120=180
6x=120+180=300
x=300:6=50
angles are 50+10=60, 2*50-40=60, 3*50-90=60
the answer is C - equilateral
8. 3x+10=5x-50
5x-3x=10+50
2x=60
x=60:2
x=30
the equal sides are 3*30+10=90+10=100
the other side is x+5=30+5=35
P=2*100+35=235
10.x+32+2x+40=180
3x+72=180
3x=108
x=108:3=36
