Question

36+z=7z+30
X+2x+3x+.....+18x=3420
100-7x=13x
8(y+10)-30=13y
100:[12+8×(3a-5)]=5
Dau coroana

Answer 1

a) 36 + z = 7z + 30 ⇔ z - 7z = 30 - 36 ⇔ -6z = -6 ⇔ 6z = 6 ⇔ z = 1
b) x + 2x + 3x + ... + 18x = 3420 ⇔ $\frac{18*19x}{2}$ = 3420 ⇔ $\frac{342x}{2}$ = 3420 ⇔ 171x = 3420 ⇔ x = 20
c) 100 - 7x = 13x ⇔ 100 = 13x + 7x ⇔ 20x = 100 ⇔ x = 5
d) 8(y + 10) - 30 = 13y ⇔ 8y + 80 - 30 = 13y ⇔ 8y + 50 = 13y ⇔ 50 = 13y - 8y ⇔ 5y = 50 ⇔ y = 10
e) 100/ [12 + 8(3a - 5)] = 5 ⇔ 100/ [12 + 24a - 40)] = 5 ⇔ 100/ [-28 +24a] = 5 ⇔ 5(-28 +24a) = 100 ⇔ -140 +120a = 100 ⇔ 120a = 100 + 140 ⇔ 120a = 240 ⇔ a = 2