Question

Știind ca a supra b egal 3 supra 7, calculati 2a+3b supra 4b

Answer 1

a/b = 3/7 =>a=3b/7

$\frac{2a+3b}{4b} = \frac{2* \frac{3b}{7} +3b}{4b} = \frac{6b+21b}{7} * \frac{1}{4b} = \frac{27b}{28b} = \frac{27}{28}$

Answer 2

a/b = 3/7
b = 7a/3
2a + 3b       2a + 3 * 7a/3     2a + 7a           9a
______  =  ___________ = ________ =   ______ =  9a * 3/28a =  
    4b               4 *7a/3             28a/3           28a/3  

= 27a/28a = 27/28