A level maths help

I've gotten to 10 = 2.1x - 0.5*a*(2.1)^2 and 10 = 1.1x + 0.5*a*(1.1)^2 for both parts respectively using suvat equations. am I on the right track?

The "u" (initial velocity) for the second phase is not the same as the "u" at the start/first phase. In fact, the initial velocity for the second phase is the final velocity from the first phase. So you can use v=u+at on the first phase to get the second phase initial velocity and solve for a (and u).
Or you could use the fact that first+second phase is 20 m in 3.2 s and use that as your second equation and then both equations would have the same initial velocity.

for the first equation I used s = 10 , u=u, a=a and t = 2.1 and for the second the same except s = 20 and t = 3.2. I use s = ut + 0.5 at^2 . I get u = 2.43 but the correct answer is 1.92

I get 1.92 so you must have made a mistake solving them. Upload your working if you need to.

Thanks I finally figured it out! Sorry for the trouble, I think it was an input error after all