verbos imperfecto y preterito
Había usar mi repuesto del último el día antes para reparar la bicicleta de mi esposa.
I translate this sentence into english as:
I had used my last spare the day before to repair my wife's bicycle.
I think the usar verb is the the infinitive form because it comes directly after a conjugated form of Haber. Is this correct?
"Había usado .... I think is correct. and I think the rest is OK.
In your school, probably yes. But remember when you are talking to person, they may or may not use the infinitive. Just wanting you to keep that in mind so that when you go to Mexico or Peru or que sea, and a person doesn't use the word as you were taught it, doesn't mean it isn't correct (for them). People don't always conform themselves to what a book may say is correct, as you witness in english all day long, they simply speak. Know what is corrrect, but maintain your flexibilty, so you don't blow a gasket when you hear something different!