math
posted by Billy on .
4c11=4c+21

move similar terms to one side.
4c=4c+32
then subtract 4c to both sides.
8c=32
then divide both sides by 8.
c=4 
4c11=4c+21
move constants to one side and variables to the other.
add 21 to both sides and add +4c to both sides.
4c+4c1121 = 4c+4c+2121
1121 = 8c
combine terms
32 = 8c
divide both sides by 8
32/8 = 8c/8
4 = c
Check my work. I always check the answer, too, by substituting into the original. In this case we have
(4*4)  11 = (4*4)+21
+1611 = 16+21
+5 = +5
GOOD. It checks.