Question 950503
a+b= 31000. Thus, a= 31000-b (1)

.07a + .10b = 2,635 (2)

Now let's substitute in (2) with what we learned in (1)

.07(31000-b) + .10b = 2,635 Now let's multiply on the left:
2170 - .07b + .10b = 2635 Next, subtract 2170 from both sides and add the left:
.03b = 465 Divide both sides by .03:
b = 15,500 This is the amount invested at 10%, and 31000-15500= 15500 is invested at .07.