el subjuntivo

Question

Qué provocar el subjuntivo en esta frase: Tendremos
que usar cuanto dinero tengamos. Es muy caro.?

Accepted Answer

Hola Sandra
This shows "something unknown"; they are talking about how much money they "may" have, therefore that uncertainty, unknown element triggers the subjunctive.
It is as if we said the same thing with a relative pronoun:

Tendremos que usar todo el dinero que tengamos.
We'll have to use all the money that we have (may have, how much that may be, we don't know)

However if we know how much money we do have you'd use the indicative:

Tendremos que usar todo el dinero que tenemos.
We'll have to use all the money that we have. (we do know here how much money we're talking about)

This lesson on relative clauses will help you see it more clearly. Have a look here.
I hope it helps.
Saludos
Inma