Translation:I will write a letter with this pencil.
Can't you omit "will" from "will write this letter" if this sentence is both present and future-tense?
Weird, I did the same and got it wrong. It can be either, you have to use context in real life.
You could, but the translation would be more like "with this pencil, i write letters".
How am I supposed to know when it is in the future? ~ます endings can be translated as future or present
You'd probably specify a future time if it wasn't meant as "presently ".
You could as well be showing your little sister's room while she's gone. She writes letters with this pencil.
I put "I will use this pencil to write a letter" and it was wrong. At first I was pouty, but then I realized that I technically added another verb, so... rip.
I had the same problem. It should still be accepted, the で particle implies some sort of use, so saying "I will use..." should still count.
Might just be my dialect of Washington English, but "I write the letter with this pencil" doesn't sound right without the "will" to me. It almost seems that "write" should be "wrote" in that sentence, which would then make it past tense (which would be wrong here)...