Question

Aflaţi termenii necunoscuţi ai proporţiilor : a) 5 supra x = 20 supra 7. b) x+1 supra 3 = 10 supra 9. Help.

Answer 1

a) 5/x=20/7
    5*7=20x
    35=20x
    x=35/20=7/4

b)  x+1/3=10/9
     (x+1)*9=3*10
      9x+9=30
      9x=30-9
      9x=21
      x=21/9=7/3

     

Answer 2

$a)\frac{5}{x}= \frac{20}{7} \\ \\ x= \frac{5*7}{20} \\ \\ x= \frac{35}{20} \\ \\ x= \frac{7}{4} \\ \\ b) \frac{x+1}{3} = \frac{10}{9} \\ \\ 9(x+1)=10*3 \\ \\ \\ 9x+9=30 \\ \\ 9x=30-9 \\ \\ 9x=21 \\ \\ x= \frac{7}{3}$