1)
p*10 = 8. Solve for the decimal fraction p: p = 8/10 = 0.80. 8 is 80% of the original 10, or, equivalently, 20% less than 10.
2) Think: 12 is half of 24, so we could immediately respond by stating that 12 is 50% less than 24.
3) 21 is what % less than 35? Think: 21 is 14 less than 35, and so taking 14/35 times 100% will give us the desired result. 14/35 = 2/5 = 40%. So, 21 is 40% less than 35.
4) 36 is 4 less than 40. Thus, 36 is 4/40 % less than 40, or 36 is 10% less than 40.