Dan has £100. Colin takes £y. How much is left

Really need on these. i have no idea what to do

"princess tower" in dubai is considered the world's tallest residential building, towering to 1 0 1 101 floors! t ( n ) t(n) models the number of tenants living on floor n n of the tower. what does the statement t ( 2 0 ) = t ( c ) t(20)=t(c) mean?

Gretchen is setting up for a banquet. she has 300 chairs and needs to distribute them evenly among t tables. how many chairs should she put at each table? write your answer as an expression.