Salil wants to put a picture in a frame. The picture is $7\frac{3}{5}cm$ wide. To fit in the frame the picture cannot be more than $7\frac{3}{10}cm$wide. How much should the picture be trimmed?

A mixed fraction can be converted into improper fraction by multiplying the denominator by whole number and adding the result to the remainder while keeping the denominator unchanged.

$7\frac{3}{5}=\frac{7\times 5+3}{5}=\frac{38}{5}$

$7\frac{3}{10}=\frac{7\times 10+3}{5}=\frac{73}{10}$

Subtract the width of the picture from the width of the frame to determine how much the picture should be trimmed.

Since $\frac{38}{5}$ and $\frac{73}{10}$ are unlike fractions.

Convert them into like fractions.

The LCM of $5$ and $10$ is $10$.

Multiply $\frac{38}{5}$ by $\frac{2}{2}$ and $\frac{73}{10}$ by $\frac{1}{1}$ to make the denominator $10$.

$=\frac{38}{5}\times \frac{2}{2}-\frac{73}{10}\times \frac{1}{1}$

$=\frac{76}{10}-\frac{73}{10}$

$=\frac{76-73}{10}$

$=\frac{3}{10}$

The picture should be trimmed by $\frac{3}{10}cm$