1)
[tex]\frac59=\frac4{a}\\5a=9*4\\5a=36 /:5\\a = \frac{36}5=7\frac15[/tex]
[tex]\frac59=\frac{5+4+c}{9+a+10}\\\frac59=\frac{9+c}{9+7,2+10}\\\frac59=\frac{9+c}{26,2}\\9(9+c)=5*26,2\\81+9c=131 /-81\\9c=50 /:9\\c = \frac{50}9=5\frac59[/tex]
2)
[tex]\frac{y}4 = \frac{5}{8}\\8y=4*5\\8y=20 /:8\\y = \frac{20}8=2\frac48=2\frac12[/tex]
[tex]\frac{x}{y}=\frac{3}4\\\frac{x}{\frac{20}8}=\frac34\\4x=3*\frac{20}{8}\\4x=\frac{60}8 /*\frac14\\x = \frac{60}8*\frac14\\x = \frac{15}{8} = 1\frac78[/tex]
3)
[tex]\frac9{40}=\frac{a+7+9}{120+40}\\\frac9{40}=\frac{a+16}{160}\\40(a+16)=9*160\\40a+640 = 1440 /-640\\40a=800 /:40\\a = 20[/tex]
