Car B accelerates at 3.5ms

In a drag Car B leaves the start line .80 secs earlier than car A.

At what time does car A pass car B?

My attempt:

Car A:

y=4.2mx

Determine constant for car B

v=u+at

v=0+(3.5)(.80)=2.8

s=1/2(0+2.8).80

s=1.12metres

Car B:

y=3.5x + 1.12

3.5x + 1.12 = 4.2x

to find when graph intercepts

-0.7x=-1.12

x=1.6 seconds

What am I doing wrong?