Answer:
This is a Spanish question involving grammar, so we have two elements that cost a certain price each:
- La camiseta roja (The red T-shirt) costs 55 pesos
- La camisa negra (The black T-shirt) costs 100 pesos
So the answer would be:
Las dos camisetas cuestan 155 pesos
Since dos camisetas is a plural form, we must conjugate the verb costar matching the third person plural, which is cuestan.