Solve these two equations for M and C, the amounts invested in munis and corporates, respectivly.

M + C = 7000

0.06M + 0.09 C = 555

Using substitution,

0.06M + 0.09*(7000 - M) = 555.

Rearranging the last equation,

0.03 M = 630 - 555 = 75

M = 75/0.03 = _____

C = 7000 - M = ____