We know that
• Astrid ate 1/8 of the pizza.
,• Her friend ate 1/2 of the pizza.
To find the total pizza eaten by them, we have to sum those fractions.
[tex]\frac{1}{8}+\frac{1}{2}[/tex]We use the following property to sum.
[tex]\frac{a}{b}+\frac{c}{d}=\frac{a\cdot d+b\cdot c}{b\cdot d}[/tex][tex]\frac{1\cdot2+1\cdot8}{8\cdot2}=\frac{2+8}{16}=\frac{10}{16}=\frac{5}{8}[/tex]