The given expression is
[tex]3\frac{3}{8}-1\frac{3}{4}[/tex][tex]\text{Use a}\frac{b}{c}=\frac{a\times c+b}{c}\text{.}[/tex][tex]3\frac{3}{8}-1\frac{3}{4}=\frac{3\times8+4}{8}-\frac{1\times4+3}{4}[/tex][tex]=\frac{28}{8}-\frac{7}{4}[/tex]LCM of 8 and 4 is 8, making the denominator 8.
[tex]=\frac{28}{8}-\frac{7\times2}{4\times2}[/tex][tex]=\frac{28}{8}-\frac{14}{8}[/tex][tex]=\frac{28-14}{8}[/tex][tex]=\frac{14}{8}[/tex][tex]=\frac{2\times7}{2\times4}[/tex][tex]=\frac{7}{4}[/tex][tex]=\frac{1\times4+3}{4}[/tex][tex]=1\frac{3}{4}[/tex]Hence the answer is
[tex]3\frac{3}{8}-1\frac{3}{4}=1\frac{3}{4}[/tex]