Answer:
x=18
Explanation:
since x+24 is in parenthesis, we need to distribute 1/2 to all the parts inside the parenthesis.
1/2 * x = 1/2x
1/2 * 24= 12
1/2x+12=21
subtract 12 from both sides
1/2x= 9
divide 1/2 from both sides
x=18
so your answer would be x=18