7.[tex]\frac{15}{21} =\frac{25}{25 +?}\\15(25+?) = 21*25\\375 + 15*? = 525\\? = 10[/tex]
8.[tex]\frac{?}{77} =\frac{30}{30+25} \\?(30+25)=77*30\\55? = 2310\\? = 42[/tex]
9.[tex]\frac{11-5}{11} =\frac{?}{22} \\22(11-5) = 11(?)\\132 = 11*?\\? = 12[/tex]
10[tex]\frac{?}{?+28} =\frac{8}{8+16} \\\frac{?}{?+28} =\frac{8}{24} \\8(?+28)=24?\\8?+224=24?\\16? = 224\\? =14[/tex]
