discount per shirt=3.66
so therefor
3x=3 times original cost per shirt
discount means minus
3x-3(3.66) since 3 discounts since 1 discount per shirt
she paid 62.31
after discount so
3x-3(3.66)=62.31
solve for x which is cost per shirt orinilally
3x-3(3.66)=62.31
divde both sides by 3
x-3.66=20.77
add 3.66 to both sides
x=24.43
cost per shirt was $24.43