To solve this problem you must apply the proccedure shown below:
1- If the triangle is a rigth triangle, you must apply the Pythagorean Theorem. Taking the length 3 inches as the hypotenuse, which is the longest side of the triangle, you have:
a^2=b^2+c^2
c=√(a^2-b^2)
b=3/4 inches
a=3 inches
2- When you susbtitute the values, you obtain:
c=√(3 inches)^2-(3/4 inches)^2
c=2.90 inches
The answer is: 2.90 inches.