Question 696725
{{{x}}} = width of the first rectangle
{{{x+5}}} = length of the first rectangle
{{{(x+5)/x=28/18}}} --> {{{18(x+5)=28x}}} --> {{{18x+90=28x}}} --> {{{18x+90-18x=28x-18x}}} --> {{{90=10x}}} --> {{{90/10=10x/10}}} --> {{{highlight(x=9)}}}
{{{x+5=9+5}}} --> {{{x+5=14}}} --> length of the first rectangle = {{{highlight(14)}}}
 
Actually, for mental math, the ratio of corresponding sides is the same and also equal to the ratio of the differences in length, so I mentally calculated
{{{x/18=5/(28-18)=5/10=1/2}}} and immediately knew that the dimensions of the first rectangle were half of the dimensions of the other one.