Question 1101491
Total amount of money invested: $30000
x+y=30000,
Total yearly interest for the two accounts is: $2280
0.07*x+0.08*y=2280
x=30000-y
Substitute for x
0.07*(30000-y)+0.08*y=2280
Multiply out
2100-0.07*y+0.08*y=2280
Combine like terms.
0.01*y=180
Isolate y
y=$18,000.00 at 8% earns $1,440 interest
x=30000-y
Calculate x
x=$12,000.00 at 7% earns $840 interest
Check
0.07*12000+0.08*18000=2280
840+1440=2280
2280=2280
If 2280=2280 is TRUE and neither x nor y  is negative then all is well
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