Again.. what is x (exponents involved)?? Help

[gmatpup]

Please explain, I thought I understood but clearly not

Thank you!!

If 2^x - 2^x-2 = 3(2^13), what is x?

A. 9
B. 11
C. 13
D. 15
E. 17


Answer is D

[LalaB]

2^x - 2^x-2 = 3(2^13)
2^x-2*(2^2-1)=3(2^13)
3*2^x-2=3(2^13)
2^x-2=2^13

x-2=13
x=15

[CollegeKart]

2^x - 2^x-2 = 3(2^13), what is x?
2^x(1-1/4)= 3(2^13)
2^x(3/4)= 3(2^13)
3(2^x-2)= 3(2^13)
x-2=13
x=15

[GMATGuruNY]

I posted an alternate approach here:

https://www.beatthegmat.com/2-x-2-x-2-3- ... 68661.html