Answer:
Explanation:
Since we know that Ivan finished all his science problems (3) we know that there are only math problems remaining
substract the science problems from the total 43-3=40
And now we can determine the amount of math problems
4/5 = 40/x where x is the total amount of math problems Ivan was assigned
cross multiply
4x = 5*40
4x=200
isolate the variable
4x/4 = 200/4
x=50
So Ivan was assigned a total of 50 math problems
(Note*) since there are 40 math problems finished 40/50 is equal to 4/5. Just a tip if you don't want to do the whole calculation
Hope this helps!