Iam very weak in this me . there are 1800 gym members in total.3/4 are aged 25 to59 years, 1/5 are over 60 years and remainder are under 25 years. how many members are under 25 years?

To solve this, we add , 3/4 + 1/5

To add fractions we different denominators we have to find a common multiple.. 4 * 5 = 20   and 5 * 4 = 20

We multiply everything by 5 (for 3/4), to get 15/20
We multiply everything by 4 (for 1/5), to get 4/20

= 15/20 + 4/20 (add the numerators)
= 19/20

If 19/20 people are 25 to 60+, 
that means 1/20 of people are under 25

We apply this to 1800 gym members:

1800 / 20        <- get's us 1/20 of 1800
= 90

There are 90 members under 25