A jet airplane reaches 833./kmh on a certain flight. How long does it take to cover 335.m? using unit conversions?

Time taken
= (335 m) / (833 km/h)
= (335 m) / [833 × 1000 m/ (3600 min)]
= 335 × 3600 / (833 × 1000) min
= 1.45 min

By "833 kmh" is assume you mean 833 km per hour

If so, the 335 m is 0.355 km (unit conversion) is 1000 m/km

Divide 0.335 by 833 and your answer will be in hours. Multiply by 60 and your answer will be in minutes.

833km/hr = 833*1000 /(60*60) = 231.4m/sec
Time to cover 335m = 335/231.4 = 1.45 seconds.