Matt needs to buy new plates for his home.  He only wants to do dishes once a week.  Three days a week it is only him and his son eating and they use 1 plate each.  On the remainder of the days, his parents join them and everyone uses 2 plates that day.  How many plates does he need to buy?
How many people are eating on the 3 days? ** So for 3 of the days, there are 1+1=2 people eating
How many plates do they use on those days? ** So for those days they use 3*2=<<3*2=6>>6 plates
How many days do the parents join them? ** On 7-3=4 days the parents join them
How many people are eating on those days? ** On those days there are 2+2=<<2+2=4>>4 people eating
How many plates do they use on those days? ** They use 4*2=<<4*2=8>>8 plates
How many plates do they use in total? ** So they use 8*4=<<8*4=32>>32 plates
How many plates do they use in total? ** That means they use a total of 32+6=<<32+6=38>>38 plates
#### 38