a-b=180
2/5 × a=30 + 3/4 × b <=> 2a/5=30+3b/4
a) b= 50
2a/5=30+3×50/4
2a/5=30+150/4
2a/5=(120+150)/4
2a/5= 270/4
8a=5×270
8a=1350=> b nu poate fi egal cu 150, deoarece numarul a nu ar mai fi natural.
b) p/100 × a=b
2a/5=30+3b/4
a=(30+3b/4)÷2/5
a=(30+3b/4)×5/2
a=150/2 + 15b/8
a=(600+15b)/8
a-b=180<=>a=180+b
(600+15b)/8=180+b
600+15b=8(180+b)
600+15b=1440+8b
15b-8b=1440-600
7b=840
b=120
a=180+b
a=180+120
a=300
p/100 × a = b
p/100 × 300 = 120
300p/100=120
3p=120
p=40
