Explain what a variable is in an addition or subtraction expression

What is y-5=3(x+1) in slope intercept form

Troy has a 7/23 balloon mortgage on his $260,000 home. he has been making payments of $1323 each month and will have a balloon payment due for the amount of $198,569.

The result of which expression will best estimate the actual product of (-4/5) x (3/5) x (-6/7) x (5/6) (i need an expression not an answer)