Applications of Linear Systems

I need help understanding this problem:

Tyrel and Dalia bought some pens and pencils. Tyrel bought 4 pens and 5 pencils, which cost him $6.71. Dalia bought 5 pens and 3 pencils, which cost her $7.12. Let a equal the price of a pen. Let b equal the price of a pencil.

**a.**Write an equation that relates the number of pens and pencils Tyrel bought and the amount he paid for them.

**b.**Write an equation that relates the number of pens and pencils Dalia bought and the amount she paid for them.

**c.**Solve the systems you wrote for parts (a) and (b) to find the price of a pen and the price of a pencil.

Thanks for helping!