Question

At Dorothy's Hair Salon, 4 gallons of shampoo will last 3 weeks. She has 7 gallons of shampoo. How much more must she order if she wants to have enough for 12 weeks?

Answer 1

so given that for 3 weeks need 4 gallons of shampoo
and for 4 time more weeks so for 12 weeks how much gallons of shampoo she need ?

but attention bc. she has 7 gallons of shampoo so what you need subtract from this given result and how many will remain so this will be the necessary ordered quantity

hope helped understandably