A) Michelle had $500 in her savings account at the beginning of the summer. Each week she took $30 out of her account. After x weeks she had taken $30x out of her account. Then $(500-30x) left in her savings account.
B) Skyler had $122 in his account at the beginning of the summer. Each week he added $24 to his account. After x weeks he had added $24x to his account. Then $(122+24x) is in his savings account.
C) If Michelle and Skyler have the same amount of money in their accounts, then
500-30x=122+24x,
-30x-24x=122-500,
-54x=-378,
x=578:54,
x=7 weeks