Question

Doughnuts are being sold in bags and cartons

A bag holds 4 doughnuts and a carton holds 10 doughnuts
Tom buys B bags of doughnuts and C cartons of doughnuts
He buys a total of T doughnuts
Write down a formula for T in terms of B and C

Answer 1

One bag holds 4 donuts, so B bags hold 4B donuts.
One cartoon holds 10 donuts, so C bags hold 10C donuts.

So, altogether
T = 4B + 10C (donuts).