(11/15а+7/12): целых 1/4=1/3

[latex]\left(\frac{11}{15}a+\frac7{12}\right):\frac14=\frac13\\\frac{11}{15}a+\frac7{12}=\frac13\cdot\frac14\\\frac{11}{15}a+\frac7{12}=\frac1{12}\\\frac{11}{15}a=\frac1{12}-\frac7{12}\\\frac{11}{15}a=-\frac6{12}\\\frac{11}{15}a=-\frac12\\a=-\frac12:\frac{11}{15}\\a=-\frac12\cdot\frac{15}{11}\\a=-\frac{15}{22}[/latex]