Răspuns:
1.
5x-7=3 | +7
5x=10 |÷5
x=2
2. x=5
2x+a=16
2×5+a=16
10+a=16
a=16-10=6
3.
[tex]x - 2y = 10 \\ (3x + y = 2 )\times 2 \\ \\ x - 2y = 10 \\ 6x + 2y = 4 \\ 7x = 14) \div 7 \\ x = 2[/tex]
4
[tex]3x - y = 10) \times - 2 \\ x - 2y = 5 \\ \\ - 6x + 2y = - 20 \\ x - 2y = 5 \\ \\ x - 6x + 2y - 2y = 5 - 20 \\ - 5x = - 15 ( \times - 1) \\ x = 3[/tex]
5.
a+b=50
a-b=10
=》 2a=60=) a=30
[tex]x + 3x + \frac{x}{4} = 170 \\ amplificam \: peste \: tot \: cu \: 4 \\ 4x + 12x + x = 170 \times 4 \\ 17x = 680 \\ x = 40[/tex]
