Are all diagonals also lines of symmetry for any given polyhon

Satchi found a used bookstore that sells pre-owned dvds and cds. dvds cost $9 each, and cds cost $7 each. satchi can spend no more than $45.

Which steps could be part of the process in algebraically solving the system of equations, y+5x=x^2+10 and y=4x-10

You are saving to buy a bicycle; so far you save 55.00. the bicycle costs 199.00. you earn 9.00 per hour at your job. which inequality represents the possible number of h hours you need to work to buy the bicycle?