calculate q when a system does 72g of work and its internal energy decrease by 90j

Answer 1

dE = q + w
72 g? of work? Is that (the g) a new unit?
If delta E decreases that means Efinal - Einitial is smaller which means energy is lost and that make the change -.
If the system does work then w is -. Substitute and solve. Post your work if you get stuck.