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

Use a calculator basically