To go to sleep, Oliver counted by 6s starting from 15. Thus the first few numbers he named were 15, 21, 21, 33...... The last number he named before he fell asleep was 363. How many numbers did Oliver name?
58 numbers. Subtract fifteen from 363 and divide the difference by six.
15 + 6n = 363 subtract 15 from both sides
6n = 348 divide both sides by 6
58 = n { plus the first number, 15 } = 59 numbers
+1443 
