Can someone teach me how to solve equations by using substitution?

my math teacher doesn't explain anything well at all and it causes me to fail every time! it's sad because others understand while i don't. i have homework on the topic but i can't even start!

begin with the basics, i'm completely lost : '(

You download a video game to your computer. you have a 60-minute free trial of the game. it takes 5 1/6 minutes to set up the game 7 1/3 minutes to play each level. you want to find out how many levels you can play for free.which inequality describes the number of levels, l, you can play in 60 minutes? can you play 6 levels during your free trial? i need ,

When solving this problem: 3025/5.5 = a/90.75 you get 49912.5 which would be the length of one of the sides of a square when the area is only 90.75 inches. is that answer correct, why, and how is it possible?

Questions 7-8. use the following table to answer. year 2006 2007 2008 2009 2010 2011 2012 2013 cpi 201.6 207.342 215.303 214.537 218.056 224.939 229.594 232.957 7. suppose you bought a house in 2006 for $120,000. use the table above to calculate the 2013 value adjusted for inflation. (round to the nearest whole number) 8. suppose you bought a house in 2013 for $90,000. use the table above to calculate the 2006 value adjusted for inflation. (round to the nearest whole number)