Three fifths in a T shirt shop are blue.

To determine the number of blue T-shirts in the shop, we need to know the total number of T-shirts available. Let's say the total number of T-shirts in the shop is represented by "x".

Given that three-fifths (or 3/5) of the T-shirts are blue, we can set up an equation:

Blue T-shirts = (3/5) * Total T-shirts

Substituting the value of "x" into the equation, we get:

Blue T-shirts = (3/5) * x

Now, if you have the total number of T-shirts, you can substitute that value in the equation and calculate the number of blue T-shirts.