suma unghiurilor este de 180 de grade, deci vom avea
a)x+30+x=180, 2x=150, x=75
b)x-42+x=180, 2x=180+42, 2x=222, x=111
c)x+3/5x=180, aducem la acelasi numitor, 5, si avem 5x+3x=900, 8x=900, x=225/2
d) avem unghi de 90 de grade, inseamna ca x+24+x=90, 2x=90-24, 2x=66, x=33
e) x+x-3=90, 2x=93, x=93/2
succes!