If I have 33 sweets what is the ratio of yellow to purple 7:4

33 sweets in a 7x to 4x ratio

7x + 4x = 33

11x = 33

x = 3

33 sweets can be put in a 7 (3) to 4 (3) ratio

which is a 21 to 12 ratio

so 21 sweets are yellow, and 12 sweets are purple to get the ratio of 7 to 4

Note:

a (b) = ab = a x b = a times b