Please help with step by step explanation

If jm equals 5x -8 and lm equals 2x -6 which expression represents jl

Find the domain of the following expression: 1/(√x)-2

Asurvey of 45 teens found that they spent an average of 25.6 hours per week in front of a screen (television, computer, tablet, phone, based on the survey’s sample mean, which value could be the population mean? 2.3 hours 27.4 hours 75.3 hours 41.5 hours