The proportion above can be solved by ensuring that they amount to the same equivalent value. Here is what i mean:
[tex]\frac{3}{7}\text{ = }\frac{3\text{ x 7}}{7\text{ x 7}}\text{ = }\frac{21}{49}.\text{ The solution to number 1 is 21 because 7x7=47, then 3 times the same 7 = 21}[/tex][tex]\frac{2}{5}\text{ = }\frac{2\text{ x 7}}{5\text{ x 7}}\text{ = }\frac{14}{35}\text{ The solution here is 35 ( 14/2 = 7, 7x 5 = 35 )}[/tex]The ratio below does not form a proportion because
[tex]\frac{4}{9}\text{ = }\frac{4\text{ x 10}}{9\text{ x 9}}\text{ =}\frac{40}{81}\text{ ( It is not proportional because the same number was not used to create the second fraction )}[/tex]