To solve this, we’ll have to use inverse operations.
Since addition is the inverse to subtraction, we’ll add 20 to 620.
20 + 620 = 640
From there, since division is the inverse of multiplication, we’ll divide .75 by 640.
640/.75 = 853.33333 repeating. We can round this to 853.33, to round to the nearest hundredth.
Therefore, 853.33 would be your answer! You can check this by solving the equation forwards (853.33 x .75 = ~640, 640 - 20 = 620.)
Hope this helps! :)