a) See below. 1.52
Convert to the same metric. So in this case, its better to convert to decimals
For this, you should use reverse bus stop. So 70 goes outside the bus stop with 21 inside.
Then add zeros on so that you can work out the answer to 2 decimal places
Then change the answer by the number of decimal places you added. So if you added 2 zeros, then your answer of eg. 70 would become 0.7