Răspuns: [tex]\bf a\cdot b-2 = 19[/tex]
Explicație pas cu pas:
Salutare!
[tex]\boxed{\bf TEOREMA\:\: \dfrac{a}{b}=\dfrac{c}{d}\Leftrightarrow a\cdot d = b \cdot c}[/tex]
[tex]\bf\dfrac{a}{3}=\dfrac{7}{b}\implies a\cdot b = 3 \cdot 7 \implies \boxed{ \bf a\cdot b = 21}[/tex]
[tex]\bf a\cdot b - 2 = 21 - 2 \implies \boxed{\bf a\cdot b-2 = 19}[/tex]
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