Answer:
f = 2 6/7
Step-by-step explanation:
[tex]\dfrac 35 \cdot f = 1 \dfrac 57 \\\\\\\implies \dfrac{3f}5 = 1 + \dfrac 57 = \dfrac{12}7\\\\\\\implies 21f = 60\\\\\implies f = \dfrac{60}{21} = \dfrac{20}7 = 2 \dfrac 67[/tex]
