Question 734894
subtracting 6 from both sides, you have

-3e^(7a+9) = -12

then divide by -3 and you get

e^(7a+9) = 4

take the natural log (ln) of both sides

ln(e^(7a+9)) = ln 4

bring down the exponent of e and we get

(7a+9)ln(e) = ln 4

note that the ln(e) is 1, so we have

7a+9 = ln(4) and

a = (ln(4) - 9) / 7 = -1.09