HELP PLEASE!!! restriction enzymes and probability?

Question

I have been told i need to use probability to work out the question below but to be honest i havent got a clue how to work this out. if anybody could give me some help as to how to work it out i would be really greatful. thanks in advance kat x*x

A DNA molecule has G+C content of 0.5 how often would you expect the following restriction enzymes to cut on average?

i)Mbo1 (recognition sequence 5' GATC 3')

ii) EcoRV (recognition sequence 5' GATATC 3')

iii) RSR11 9recognition sequence 5' CGG(A/T)CCG 3')

Answer 1

i) Mb01 probability 1/3 x 0.5

ii) EcoRV probability 1/3 x 0.5

iii) RSR11 probability 1/3 x 0.5