each cat will eat 3/4 of a tin of food every day
paul is going to be away for 7 days
what is the least number of tins needed to feed 2 cats
one cat eats $\displaystyle \frac {3}{4}$ tins of food per day
so two cats will eat $\displaystyle 2 \times \frac {3}{4} = \frac {3}{2}$ tins of food per day
so for 7 days, the cats will eat $\displaystyle 7 \times \frac {3}{2} = 10 \frac {1}{2}$ tins of food
so need need to have at least 11 tins of food