COULD YOU PLEASE EXPLAIN TO ME INTO DETAILS ABOUT THIS MATH WORD PROBLEM?

1.5s + 2p = amount she makes

1.5 ( 1.50) + 2( 2.00 ) = amount she makes... $6.25

How can she sell 1/2 a shirt?? ( .5)

The amount from selling both kinds of clothes is the sum of two terms. The first is the amount from shirts. The second is the amount from pants. 

This is a typical mixture problem. 

You have two quantities of stuff. Each has its own price. 

For each, its value = quantity x price. Total value = value of first + value of second. Also total quantity = quantity of first + quantity of second. 

In various forms these give rise to two equations in two unknowns. 

In your problem, how much she made on shirts = number of shirts sold x price per shirt. 

(Which of WHAT following statements?)

The amount she made from selling shirts is $1.5s.