Similar triangles: the shortest side of triangle $B$ measures $6$. Find the other two sides. Two triangles are similar. Triangle $A$ has sides measuring $3$, $4$, and $5$. The shortest side on triangle $B$ measures $6$. What are the lengths of the other two sides of triangle $B$?

Let larger side of triangle A is XY = 5, smaller side YZ = 3 and other side XZ = 4.
Now sides of triangle B let larger side PQ = a, smaller QR = 6 and other side PR = b.
Now two triangle are similar so their sides are in proportion.
$\frac{PQ}{XY} = \frac{PR}{XZ} = \frac{QR}{YZ} $
Then you can find other two sides of B.
$\frac{a}{5} = \frac{b}{4} = \frac{6}{3} $
So we have,
$\frac{a}{5} = \frac{6}{3} $
a = 10
Also,
$\frac{b}{4} = \frac{6}{3} $
b = 8

Or you can do like this also,

Smaller side of triangle B is twice than smaller side of triangle A. And similar triangle are in proportion. So you can twice remaining two sides of triangle A to get remaining sides of triangle B.
