i need help with this question

Question

The combined yearly interest for x dollars invested at 12% and 20,000-x dollars invested at 7% is(Use integers or decimals for any numbers in the expression.)

Answer 1

there seems to be some missing information in this problem, such as how much interest was earned.

Let's call it 20000R

.12x + .07(20,000-x) = 20000R where R= average return .07<R<.12, maybe about 10%

= .12x -.07x + 1,400 =20000(.10) = 2000

= .05x + 1,400 = 2000

.05x = 2,000-1400 = 600

x = 600/.05 = $12,000 invested at 12%, $8,000 invested at 7%

.12(12000)+.07(8000) = 14400+5600 = $2,000 total interest