Question 507873
-6p - 21 = 3p - 12
Add 21 both sides of the above equation
-6p - 21+21 = 3p - 12 + 21
Cancel out 21 from left hand side
-6p = 3p + 9
Subtract 3p from both sides of the above equation
-6p -3p = 3p - 3p + 9
Cancel out 3p from right hand side
-9p =9
Divide by -9 both sides of the above equation
-9p/-9 =9/-9
Cancel out 9 from both sides
p=-1

Check
Put the value of p in original equation
-6p - 21 = 3p - 12
-6(-1) - 21 = 3(-1) - 12
6-21=-3-12
-15=-15