Find the product and simplify your answer -4a^4(9a^2-8)

Tracy solved the following problem. which of the statements is true? 9 ÷ 3 + 6 × 2 3 + 6 × 2 9 × 2 18 her answer is correct. her answer is incorrect. she should have multiplied before dividing. her answer is incorrect. she should have multiplied before adding. her answer is incorrect. she should have added before dividing.

How to do this , and can some one explain

Asystem of equations has 1 solution.if 4x-y=5 is one of the equations , which could be the other equation ?