y = a + t(x-3), make 'x' the subject

```
y - a = xt - 3t 
y -a + 3t = xt            :divide t on both sides
y -a + 3t/t = x           :this is my answer

```

but the real answer should be 

```
x = 3 + y-a/t      :i don't know why the 3 has no 't' in this answer.

```