La camiseta roja cuesta cincuenta y cinco pesos. la camista negra cuesta cien pesos. ? cuanto cuestan las dos camistas?

será 155 para las dos camisetas

Serán 155 pesos por ambas camisetas.

I'm not sure if you mean for us to translate or to answer. but i'll translate as these are questions for you to answer. 1. how long has it been since you've read a book? . 2. how long has it been since you've eaten breakfast? . 3. how long has it been since you've talked with your spanish professor?

Incorrect. the right answer is "su nieto estudia la lecciòn"