Lois used 3/5 of a can of tuna in the afternoon and 1/4 of that can in the evening. At the end of the day how much of the can was left

7/20

Step-by-step explanation:

You have: 3/5 - 1/4

When you have different denominator:

1) Multiply in cross. The numerator of the first fraction is multiplied by the denominator of the second, and the denominator of the first by the numerator of the second. Both multiplications are subtracted.

3/5 - 1/4 = [ (3*4) - (5*1) ] / ...

2) The denominators of the two fractions are multiplied.

3/5 - 1/4 = [ (3*4) - (5*1) ] / (5*4)

3) Resolve operations

= (12-5) / 20

= 7/20