Algebra 2 Logarithmic Function PLEASE HELP?

Change f(x) to y then switch the y and the x. Just change places the solve for y. Sounds weird but it is correct.4.7x=21 Base Number Exponent. So log 4.7 but 4.7 needs to be like an exponent on the bottom. Then 21 next to it so it will look like log 4.7 21 remember the 4.7 is small on bottom. Then on question 7 just divide by 2 on both sides so the answer is 4.5 that all I can remember srry