1. 3/4+1/5 Change both denominator to the same- 4*5=20 So far its: ?/20 + ?/20
2. For the first fraction (3/4) we do 3*5=15 Because when we found the denominators we multiplied each denominator by each other. For the second one we do pretty much the same. We do 1*4=4.
3. The final equation is 15/20 + 4/20. Now add both numerators, which is 19. You leave the denominator as it is. So the final fraction is 19/20.
4. Next to get a full fraction from 19/20 you need 1/20 to get 20/20=1. On the calculator you type in: 1/20*1800 OR... 1800/20 OR... (18/2)100
So the final answer is 90. 1800/20=90 = 90 members under the age of 25.