server to cook ratio is 5 : 2......added = 7
this means that 5/7 of the cooks and servers are servers and 2/7 of the cooks and servers are cooks
so if the total cooks and servers is 42..
5/7 * 42 = 210/7 = 30 of them are servers <===
2/7 * 42 = 84/7 = 12 of them are cooks
