Answer:
4. x=10
5. x=15
6. x=20
7. x=4
Step-by-step explanation:
4. 50+4x=90
90-50=40
40/4=10
x=10
5. (2x+60)+6x=180
6x+2x=8x
8x+60=180
180-60=120
8x=120
120/8=15
x=15
6. 3x+30=90
90-30=60
60/3=20
x=20
7. (8x+120)+7x=180
8x+7x=15x
15x+120=180
180-120=60
15x=60
60/15=4
x=4
