Question 1010657
<pre>
{{{3/2}}}{{{""=""}}}{{{15/10}}}

Multiply the upper left number by the lower right number, get 3×10=30
Multiply the upper right number by the lower left number, get 15×2=30
They are the same, so this is a proportion.

{{{17/4}}}{{{""=""}}}{{{85/20}}}

Multiply the upper left number by the lower right number, get 17×20=340
Multiply the upper right number by the lower left number, get 85×4=340
They are the same, so this is a proportion.


{{{8/3}}}{{{""=""}}}{{{48/18}}}

Multiply the upper left number by the lower right number, get 8×18=144
Multiply the upper right number by the lower left number, get 48×3=144
They are the same, so this is a proportion.

{{{11/13}}}{{{""=""}}}{{{66/91}}}

Multiply the upper left number by the lower right number, get 11×91=1001
Multiply the upper right number by the lower left number, get 66×13=858
They are NOT the same, so this is NOT a proportion.

Edwin</pre>