M2 projectile Q help

Find an expression in terms of t for the horizontal displacement of each and equate

Is that box an unknown angle

If so do the same for vertical displacement

2 equations in 2 unknowns, solve simultaneously

box isnt unknown, cos=4/5
and i tried that, if we use the s=ut+0.5at^2 equation with horizontal motion, both equations give s=28t.
and with vert, i get s=0.5gt and s= 21 - 0.5gt^2 which doesnt give the correct ans when equating.

That first s should be negative

so -s=0.5gt^2 and s= 21 - 0.5gt^2? but that would give no solution.

21t

I get t=3.74

say the answer is t=3.5

say the answer is t=3.5

Yep 3.5

With a diagram it is clear

Downward displacement of A plus upward displacement of B = height of cliff

Crazy I'm using an 11 year old post to do my hwk!!

Crazy I'm using an 11 year old post to do my hwk!!

hello is there any chance you can help me with this question part b