Answer:
The area increases by 6 square units.
Explanation:
The formula for the area of a triangle is base times height divided by two.
So, first solve 3 times 4 divided by 2.
Simplify 4 and 2 and you get 3 times 2 which = 6
Then Mark doubles it right?
So do 6 times 2 and you get 12
The first answer is 6, so it increased by 6.
I hope this answer helped. Sorry if I was wrong.