___:21=5:7 helppp me pleasee

How do i do this? i don’t understand

Me d is also an option but i couldn't get it in the picture

Order the equations from least to greatest based on the number of solutions to each equation.-4^x -1 = 3^(-x) – 2 -3x + 6 = 2^x+13^x – 3 = 2x - 2