Question 431993
Let X equal the CD deposit,Y the savings bond deposit:

X+Y=12,000
.04X+.07Y=720
Multiply the second equation by 100:
4X+7Y=72000
4X+4Y=48000
Subtract the second from the first , we get:
3Y=24000
Y=8000

If Y=8000, then X=4000.