The variable m is the number of minutes. So m=3 means the number of times an adult blinks in 3 minutes and to find that number we put the number 3 where m appears in the expression 10m+3. So the answer when m=3 is 10*3+3=30+3=33 blinks. In two hours there are 120 minutes, so m=120 and the expression gives us 10*120+3=1203 blinks.