Projectile Motion Long Jump Help

[singlish]

An athlete executing a long jump leaves the ground at a 30 degree angle and travels 7.80m.
(a). What was the takeoff speed?
(b). If this speed were increased by just 5.0 percent, how much longer would the jump be?

I'm having some troubles with part a. I've been struggling to comprehend projectile motion and I've been trying to find T using different methods but none of them work. I eventually came up with 9s using cosine, but I can't find initial velocity now. Any advice or tips would be appreciated.

 

[Harmony]

x=(ucos30)t
t=2usin30/g
R=(u^2sin(2*30))/g

 

[eureka360]

guys.. can you please help me with this simple problem my instructors gave us for home work... its about projectile motion..

what is the time if the displacement is at 21 meters having a 35degrees angle with the original velocity of 100m/s.