Help? I don't understand how to do this. Help ASAP

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

Which expression do you get when you eliminate the negative exponents of 4a^2 b^216a^-3 b

Find the perimeter of the triangle with vertices  d(3, 4),  e(8, 7), and  f(5, 9). do not round before calculating the perimeter. after calculating the perimeter, round your answer to the nearest tenth.