Answer:
1/30 of a ton
Step-by-step explanation:
Write this as an expression:
1/3 of a ton and 1/2 of a ton were taken to the site.
4/5 of a ton were remove from the site.
Amount of a ton at the site = 
Solve the equation by finding <u>common denominators</u> (when the bottom numbers are the same).
Focus on the first part. The least common multiple (LCM) of 3 and 2 is "6", which will become the denominator.
For <u>1/3 to become ?/6</u>, multiply top and bottom by 2.
For <u>1/2 to become ?/6</u>, multiply top and bottom by 3.

Now we can add the numerators together over the same denominator.

Do the same thing as before and change the denominators. The LCM of 6 and 5 is "30".
For <u>5/6 to become ?/30</u>, multiply top and bottom by 5.
For <u>4/5 to become ?/30</u>, multiply top and bottom by 6.

Subtract the numerators:
Answer in tons
Therefore there was 1/30 of a ton of rock left at the construction site.