PLS HELP ASAP!! Mary’s weekly allowance is $8 and David’s weekly allowance is $5. Every week they each spend $2 on lunch. Write a numerical expression to show how many weeks it will take them together to save enough money to buy a video game for $45. 

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

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

The tuition costs, c, for a local community college are modeled by c(h) = 250 + 200h, where h represents the number of credit hours taken. the local state university has tuition costs, s, modeled by the function s(h) = 300 + 180h. how many credit hours will a student have to take for the two tuition costs to be equal? round the answer to the nearest tenth of an hour.