Question 479558
a:b=9:4 => {{{a/b=9/4}}} => {{{a=(9/4)b}}}
b:c=5:3 => {{{b/c=5/3}}} => {{{b=(5/3)c}}}
{{{a=(9/4)b=(9/4)*(5/3)c=(15/4)c}}}
(a-b) : (b-c)={{{(a-b)/(b-c)=((15/4)c-(5/3)c)/((5/3)c-c)=cross(c)(15/4-5/3)/cross(c)(5/3-1)=((15*3-5*4)/12)/((5-3)/3)=(25*3)/(12*2)=25/8}}}=25:8