А)3 целых 3/4+ 1 целая 1/2= б) 2 целых 5/6-1 целую 5/12= в) 4 целых - 1 целую 2/3= г) 3...

А) $3\frac{3}{4}+1\frac{1}{2}$ = $\frac{15}{4}+\frac{3}{2}$ = $\frac{15}{4}+\frac{6}{4}$ = $\frac{21}{4}$ = $5\frac{1}{4}$ = $5,25$ ;
б) $2\frac{5}{6}-1\frac{5}{12}$ = $\frac{17}{6}-\frac{17}{12}$ = $\frac{34}{12}-\frac{17}{12}$ = $\frac{17}{12}$ = $1\frac{5}{12}$ ;
в) $4-1\frac{2}{3}$ = $3\frac{3}{3}-1\frac{2}{3}$ = $2\frac{1}{3}$ ;
г) $3\frac{2}{7}-\frac{6}{7}$ = $\frac{23}{7}-\frac{6}{7}$ = $\frac{17}{7}$ = $2\frac{3}{7}$ ;
д) $1\frac{1}{3}*4$ = $\frac{4}{3}*4$ = $\frac{16}{3}$ = $5\frac{1}{3}$ ;
е) $3\frac{1}{4}*\frac{2}{5}$ = $3,25*0,4$ = 1,3 = $1\frac{3}{10}$ ;
ж) $2\frac{1}{4}:3$ = $2,25:3$ = $0,75$ = $\frac{3}{4}$ ;
з) $20:2\frac{1}{2}$ = $20:\frac{5}{2}$ = $20*\frac{2}{5}$ = $4*2$ = $8$ .