In spanish how can the verb tener be used?

Is anyone able to ? i am so confused. this sheet is about irregular preterit verbs and direct object pronouns in spanish.

2. choose the answer that best completes the sentence. tú (entregar) los libros. (2 points) a : entrego b : entregas c : entrega d : entregan

Achemist mixes 4 liters of one acid solution with 10 liters of a 40% solution, resulting in a 30% acid solution. what is the value of x, the acid concentration of the first solution