Answer:
54,400
Step-by-step explanation:
Let x be the amount he invests at 6%
1280 = 0.06x + 0.07(20000 - x)
1280 = 0.06x + 1400 - 0.07x
1280 - 1400 = -0.01x
-120 / -0.01 = x
x = 12000
Therefore, he invests $12,000 at 6% and $8,000 at 7%
Answer:
x=7
Step-by-step explanation:
3(2x - 5) = 9(10 - x)
6x-15=90-9x
6x+9x=90+15
15x=105
x=7