Question 198105
Well, that depends whether the missing side is the hypotenuse or not
If the missing side is the hypotenuse (always the longest side), then, by the Pythagorean theorem ({{{c^2=a^2+b^2}}}), the missing side (c) must be 5 inches long because in this right triangle...
{{{5^2 = 3^2+4^2}}}
{{{25 = 9+26}}}
But, if the missing side is not the hypotenuse, then the hypotenuse must be the 4-inch side, so, let the missing side be a, then, by Pythagoras...
{{{4^2 = a^2+3^2}}}
{{{16 = a^2+9}}}
{{{a^2 = 7}}}
{{{a = sqrt(7)}}}inches.