Logarithmic equations driving me crazy...

logarithmic equations with fractions and exponents calculations

I tried to type inn the equations here but I can't type exponents

If any one has Kaplan see page 148 example 1.

Here's a narrative

Log I = Log 10 exponent -16 + 9 (I can't figure out how the logs got dropped see below)

I = 10 exponent -16 x 10 exponent 9 = 10 exponent -7 watt/cm sq

Please help....! I'm going bankers with these dropping log calculations.