Question

the acceleration of gravity on the surface of Mars is m/s squared. if an astronaut in a space suit can jump upward 20cm on the earth's surface, how high could he jump on the surface of Mars?

You need to provide a number for the acceleration of gravity on Mars, which I will call g'. If they did not provide that number to you, you can look it up or compute it from G, Mmars and Rmars.
g' = G* Mmars/(Rmars)^2
G is the universal constant of gravity.

(Broken Link Removed)
has the value you seek.

An astronaut on Mars can jump up a distance 20 cm * (g/g'), where g is the acceleration of gravity at the surface of the earth (9.8 m/s^2) and g' is the value at the surface of Mars.