Increasing and Decreasing Amounts by a Given Ratio

Decrease $32$ in the ratio $3:4$.

Increase 20 in the ratio 3 : 2.

In a mixture of $126$ litres of milk and water, milk and water are in ratio $5:2$. $24$ litres water must be added to the mixture to make this ratio $3:2$.

The bus fare between two cities is increased in the ratio $7:9$. Find the increase in the fare, if the increased fare is $\$225$?

The bus fare between two cities is increased in the ratio $7:9$. The increase in the fare is $\$b$, if the original fare is $\$210$. Find the value of $b$.

Cotyledons are also called-