To work this out you would first need to find how many times 5% goes into 100%, You can do this by dividing 100 by 5, this gives you 20. This is because the whole amount is equivalent to 100%.
To work out the total number of readers you would multiply 70 by 20, this gives you 1400. This is because we know that 70 is equivalent to 5% and that 5% goes into 100% 20. So by multiplying 70 by 20 we are working out the total (100%), and that this shows us there are 1400 readers.
Because the side has to be increased by 50% you find half of 8, which is 4 and you add 8+4 because you add the increased amount 8+4=12 you then just find the area.... so 12x12= 144