Ответ:

[tex]1\frac{7}{8} *12:\frac{3}{4} =\frac{15*12}{8} :\frac{3}{4} =\frac{15*3}{2} :\frac{3}{4} =\frac{45}{2} :\frac{3}{4} =\frac{45*4}{2*3} =15*2=30[/tex]