Question 948269
Similar triangles have sides that are {{{proportional}}}. 
The shortest side of the first rectangle is {{{5}}}, so that corresponds to the shortest side of the new one which is {{{15}}}. 
The side lengths are {{{5}}} and {{{15}}}, so the ratio is {{{1}}} to {{{3}}}. 

The longest side length of the first triangle is {{{10}}}, so the longest side of the new triangle must be three times that, or {{{30}}}.

The third side of the first triangle is {{{6}}}, so the third side of the new triangle must be three times that, or {{{18}}}

check ratios:

{{{5/15=6/18=10/30}}}
{{{0.33=0.33=0.33}}}