I need help on these questions asap.

23%; £80; 300; 4

Step-by-step explanation:

19. First, we'll work out what Rob earned on the telescope. That's (£). Next we'll use the formula for profit %, profit over cost price, so that would be

Which is 23%.

20. Let the original price be £. Then we have

(£)

21. a) Let the original population be people. Then we have

(people)

b) We'll assume that there are years before that happens. We know that the population grows by 60 each year, so

(years)

sin3a=12/15

step-by-step explanation:

since one side was multiplied by 3 the other side must also be multiplied by 3.