Помогите пожалуйста.

Решите задачу:

$a)15 +(347 - (87 - 85 \div 17) \times 3 + 4) \div 3 = 50$
$15 + (347 - (87 - 5) \times 3 + 4) \div 3 = 15 + (347 - 82 \times 3 + 4) \div 3 = 15 - (347 - 246 \div 4) \div 3 = 15 + 105 \div 3 = 50$
$б) {56}^{2} = 3136$
$в) {302}^{2} = 91204$
$г) {9}^{3} = 729$ $д)4 \times {3}^{3} - ( {21}^{2} \div 7)^{2} \div 49 = 4 \times 27 - \frac{ \frac{ {21}^{4} }{ {7}^{2} } }{49} = 108 - \frac{ {21}^{4} }{2401} = 27$