a)
\(\frac{1}{2}-0,25+0,2\)
\(=\frac{1}{2}-\frac{1}{4}+\frac{1}{5}\)
\(=\frac{10}{20}-\frac{5}{20}+\frac{4}{20}\)
\(=\frac{10-5+4}{20}\)
\(=\frac{1}{20}\)
b)\(\frac{7}{6}-0,875+0,7\)
\(=\frac{7}{6}-\frac{7}{8}+\frac{7}{10}\)
\(=\frac{140}{120}-\frac{105}{120}+\frac{84}{120}\)
\(=\frac{140-105+84}{120}\)
\(=\frac{119}{120}\)