a) lipseste necunoscuta ...
o varianta posibila ar fi: 7x/5 = 3 intregi si 4/15
7x/5 = (3*15+4)/15
7x/5 = 49/15 => 15*7x=5*49
de unde x = (5*49)/(15*7)=7/3∈Q ;
b) 5x/18 - 5/3 = 7/12 | ×36 (numitorul comun...)
10x - 60 = 21 => 10x = 81 deci x = 8,1∈Q ;