Let y and z be two of the side lengths of a triangle. The length of the third side x cannot be any number. It must satisfy all the following restrictions:
x + y > z
x + z > y
y + z > x
Combining the above inequalities, and provided y>z, the third size must satisfy:
y - z < x < y + z
We are given the measures y=10, z=9. The third side must satisfy:
If you divide the 10 pages she has read by the total 15 pages, you get 0.66. Another way to get this is to put 10 over 15. Divide both the numerator and denominator by 5 to get 2/3.