Odpowiedź:
4)
x + x+3 = 15 zł
2x + 3 = 15
2x = 15-3
2x = 12
x= 12/2
x= 6
x - szklanka soku
5)
x + y = 68 zł
x-5 = 2y
y = (x-5)/2
x + ((x-5)/2) = 68
x + x/2 - 5/2 = 68
3/2x = 68-2,5
3/2x = 65,5
1,5x= 65,5
x = 65,5/1,5
x = 65 i 1/2 / 3/2
x= (131/2) / 3/2
x= 131/2 * 2/3 = (131*2)/2*3 = 162/6 = 27
y = (27-5)/2 = 22/2 = 11
odp. Kubek kosztuje 11 zł
6)
4x-9x = -15
-13x = -15
x= -15/-13
x= 15/13
7)
I. x/11 + 5/11 = 1
x/11 = 6/11
x=6
II. x^2 - 6x * (3x + 6) = 0
3x +6 = 0
3x = -6
x= -2
lub
x^2 - 6x = 0
x^2 = 6x
x = 6
III. 5x = -30
x = -6
IV. -6x-x = -34 - 8
-7x = -42
x = 6
