Answer
1.7
Work Step by Step
Use the Pythagorean Theorem to find the missing length.
$a^2+b^2=c^2\longrightarrow$ substitute the given values
$0.8^2+1.5^2=c^2\longrightarrow$ simplify exponents
$0.64+2.25=c^2\longrightarrow$ add
$2.89=c^2\longrightarrow$ find the square root of each side
$\sqrt{2.89}=\sqrt{c^2}\longrightarrow$ simplify
$1.7=c$
