a. If he pays 15% in taxes, that means that he recieves 85% of his paycheck. We can calculate this percentage using a rule of three:
This way,

His paycheck after taxtes is $697
b. He can expect to recieve 3/4 of his regular paycheck, or 75%. We can also calculate this percentage using a rule of three:
Therefore,

He can expect to recieve $522.75
c. If he gets a 10% raise, it means he'll get 110% of his $679 4-week paycheck. We'll use a rule of three again,
This way,

He will recieve $746.90 after the 10% raise