Bonjour je suis en 4ème, pouvez vous m’aider svp. Merci d’avance

A = [tex]\frac{21}{8} -\frac{5}{8} *\frac{3}{10}[/tex]

= [tex]\frac{21}{8} -\frac{15}{80}[/tex]

= [tex]\frac{210}{80} -\frac{15}{80}[/tex]

= [tex]\frac{195}{80}[/tex]

= [tex]\frac{195:5}{80:5}[/tex]

= [tex]\frac{39}{16}[/tex]

B = [tex]\frac{1}{2} + \frac{9}{10} * \frac{5}{21}[/tex]

= [tex]\frac{1}{2} + \frac{45}{210}[/tex]

= [tex]\frac{105}{210} + \frac{45}{210}[/tex]

= [tex]\frac{150}{210}[/tex]

= [tex]\frac{150:5}{210:5}[/tex]

= [tex]\frac{30}{42}[/tex]

= [tex]\frac{5}{7}[/tex]

C = [tex]\frac{15}{4} + \frac{5}{12} :\frac{10}{9}[/tex]

= [tex]\frac{15}{4} + \frac{5}{12} *\frac{9}{10}[/tex]

= [tex]\frac{15}{4} + \frac{45}{120}[/tex]

= [tex]\frac{15*30}{4*30} + \frac{45}{120}[/tex]

= [tex]\frac{450}{120} + \frac{45}{120}[/tex]

= [tex]\frac{495}{120}[/tex]

= [tex]\frac{495:5}{120:5}[/tex]

= [tex]\frac{99}{24}[/tex]

= [tex]\frac{33}{8}[/tex]

D = [tex]5*\frac{9}{10} -\frac{7}{10}[/tex]

= [tex]\frac{45}{10} -\frac{7}{10}[/tex]

= [tex]\frac{38}{10}[/tex]

= [tex]\frac{19}{5}[/tex]