In order to find the value of a ratio, you have to find one part of the ratio. In order to do this, you have to add the two values (2+7), that you split the ratios in, which gives you 9. You then divide this by the amount, which is £72. £72/9= £8. Therefore, one part is £8. In order to find what each one is worth, you have to multiply each part of the ratio by £8.
£8x2= £16, £8x7= £56.
Therefore, £72 split into the ratio of 2:7 is £16:£56
Hope this helps :)