Which expression is equivalent to 6x³+y²-5x³+2y²​

Step-by-step explanation:

6x³ and (-5x³) are like terms

y² and 2y² are like terms

Combine like terms

6x³ + y ² - 5x³ + 2y² = 6x³ - 5x³ + y² + 2y²

                                 = x³ + 3y²

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.