Which strategy can be used to multiply 6 times 198 mentally

The vet charges $45 for an office visit and $10 for each vaccination your dog needs. write an eaquation

The volume of a sphere is increased by 6%. calculate the corresponding percentage increased in it area.

Money off coupons have been circulated to 300 households. only 2/5 of these were redeemed (used) in the local supermarket to get a free shampoo. what fraction of coupons were unused? (ps: write how you got the answer)