Callum either walks to school or travels by car.
The probability that he walks to school is 0.65. If he walks to school, the probability that he
will be late is 0.3
If he travels to school by car, the probability that he will be late is 0.05
Work out the probability that he will not be late.
Draw a probability tree diagram. The opposite of 0.65 is 0.35 as it must add to 1. then you can do the same with the other 2. multiply them and add and you get 0.7875