Answer:
Mary drew 66 buildings and Tess drew 33 buildings.
Step-by-step explanation:
Let's label the number of buildings drawn by Mary as x and the number of buildings drawn by Tess as y.
We know there are 99 buildings drawn. This means
99=x+y
We also know that Mary drew twice as many buildings as Tess. We can represent this as
x=2y
Now, let's substitute x for 2y, since that would put us in common terms
99=2y+y
Add common variables together and you get
99=3y
Solve for y by dividing 99 by 3
y=33
We now know that Tess drew 33 buildings, as well as y=33. Substitute y in the equation for how many buildings Mary drew:
x=2(33)
Now we know that Mary drew 66 buildings.
To check our work,
99=x+y
99=66+33
99=99
