33000 dollars was invested. part at 4% and part at 7%. for the period of one year. the annual interest was 1950 dollars. how much was invested at each rate?

Inv1 investment 1
inv2 investment 2
A) inv1 + inv2 = 33,000

B) .04 inv1 + .07 inv2 = 1,950

Multiplying A) by -.04

A) -.04 inv1 - .04 inv2 = -1,320      
Then adding B)
B) .04 inv1 + .07 inv2 = 1,950

.03 inv2 = 630
inv2 = 630 / .03
inv2 = 21,000 invested at 7%
inv1 = 33,000 -21,000= 
12,000 invested at 4%