I need help

Question

12^x-2=20

Answer 1

When you have the variable in the exponent you need to think about taking the logarithm of both sides of the equation.  If the problem is  12^x-2 = 20  then  

 

ln(12^x-2) = ln(20)  

(x-2)*ln(12) = ln(20)

x - 2 = ln(20)/ln(12)

x - 2 = 1.2056

x = 3.2056  

 

Check:  12^3.2056-2 = 12^1.2056 = 20.001 ~ 20  

 

I have done the problem using the natural logarithm ln but if you're more comfortable with base 10 logarithms they will work just as well.