Before solve this question, we should understand the about the word 'of' mean in math. Actullay the The word "of" is use in math for repetition or some time use for quantify in theoretical math question and word problems.

For example if 2 items are in 10 boxes then we write it as '2 items of 10 boxes'. For find their totals we multiply 2 by 10 and get 20 as total items. We can say that 'of' mean multiplication in math. But it is not only multiplication it is use for represent quantity. We should solve the 'of' word before multiplication and and division.

It is same as 2.3^4 Here 3^4 mean multiplication of 3 with four times (i.e 3*3*3*3) and 2 is also very close to 3 ready for multiply but we solve the exponent before multiplcation and we cannot multiply 2 by 3. First we solve exponent (3^4=3*333 =81) then multiply by 2. (2.3^4=2.81 = 162).

Similary
100 ÷ 4 of 5 (Solve the 'Of')
= 100 ÷ 20 (Solve the division)
= 5

Some people also convert the word 'of' in multiplcation sign then they solve it (multiplication and division) from left to right. but their is 'of' word in question there is not multiplication sign. Math expert should research on it and discuss. My view are as above.

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Note

In above question we are applying BODMAS rule
B for bracket, O for Order/Of, D for Division, M for Multiplication, A for Addition, S for Subtraction