G(t)=2t-0,25 0<=t<=t_1

G(t)=1,6t+2,15 6<=t<=t_2

So I just wanna know how I could calculate what t would be when y axe = 25

Typing this into a tool works perfectly, and the result would be: t = 14,29 when y = 25, but I just don't know how I could calculate this on paper.