How to write a binomial expression in standard form that has a degree of 4

(x+a)^4 = ^4C_0 x^4 + ^4C_1 x^{4-1} a + ^4C_2x^{4-2}a^2 + ^4C_3x^{4-3}a^3 + ^4C_4x^{4-4}a^4

= x^4 + 4x^3a + 6x^2a^2 + 4xa^3 + a^4

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.