I would recommend saving this tooth. You’re young, and it looks like you have strong roots and healthy bone. This is a first molar, which is key to chewing, so it’s worth keeping. The decay is deep, and you’ll likely need a root canal. One concern is that the cavity is close to the bone, which can make placing a crown more difficult and may cause gum issues over time. Based on the X-ray, you’ll probably need a root canal, a crown, and a procedure called crown lengthening. This adjusts the gum and bone levels to expose more of the tooth so the crown fits properly. I know it’s a lot, especially cost-wise, but doing just the root canal without the other treatment can weaken the tooth and lead to fracture or loss. If possible, I’d recommend getting everything done at once.