Acestea sunt exercitiile

15. 2x / 3y = 1 / 2
2x * 2 = 3y * 1
4x = 3y
x = 3y / 4
x / y = ( 3y / 4) / y = 3y / 4y = 3/4
16. 3a=1<=> a=1/3
5b=2<=> b=2/5
(2/3+6/5)/4( 2/3-2/5) aducem totul la acelasi numitor=>28/15 ori 4 ori 15/4=28