Bonsoir,
[tex]3 \times \frac{5}{4} + 7\times \frac{9}{8} = \frac{15}{4} + \frac{63}{8} = \frac{15\times 2}{4\times 2} + \frac{63}{8} = \frac{30}{8} + \frac{63}{8} = \boxed{\frac{93}{8}}[/tex]
[tex]\frac{5}{2}\times 9 - \frac{3}{4} \times 7 = \frac{45}{2} - \frac{21}{4} = \frac{90}{4} - \frac{21}{4} = \frac{90-21}{4} = \boxed{\frac{69}{4}}[/tex]
Bonne soirée.
