make the letter in the bracket the subject of the formulae:

Question

v=u-3t (t)
a=b-4c (c)

Answer 1

Rearrange the equaqtion as follows.
3t = u-v
t = (u - v)/3
Do the other the same way.

Answer 2

make v the subject of the formulae:

v=2v+3u

Answer 3

Nabby's advice and equation are wrong.

Answer 4

i meant V=2v+3u

make the small v the subject of the formulae

Answer 5

It is confusing if you change your name and add additional questions to the same thread. Your questions then look like attempted answers. Start a new question. Uing both upper and lower case of the same letter in an equation is not advised in algebra, although physicists have to do it quite often.