Please answer fast! :)

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?

In the equation sqrt(n+5)-sqrt(11-10)=1. what is the value of n

Light travels at 186,000 miles per second. light takes about 1 1? 3 seconds to travel from the earth to the moon. calculate the distance between the earth and the moon based on the speed of light.