5biscuits cost 30p altogether how much do 7 biscuits cost

42p Because 5/30 is 6, and 6*7= 42 Hope this helps :)

First, find out how much one biscuit costs.  As there are 5 biscuits, you divide the total (30) by 5.  30 / 5 = 6.  One biscuit costs 6p. 

Now that you know how much one biscuit costs, you times your result by 7.  6 X 7 = 42.  7 biscuits cost 42p.