Карточка 1. Решите уравнения: 1) 5x = 105; 2) 12x + 16 = 88; 3) 8 + 21x = −5 + 16x; 4) 4(x + 7) = −3(15 − 3x); 5) 1,6x − 2,5 = 0,2 + 1,98; 6) 3,64 + 4,7x = 6,4(0,2x − 0,5); 7) 5/7 x − 4/5 = 23/25 + 3/14 x.

1. \(5x=105\)

   \(x=105:5=21\)

2. \(12x+16=88\)

   \(12x=88-16=72\)

   \(x=72:12=6\)

3. \(8+21x=-5+16x\)

   \(21x-16x=-5-8\)

   \(5x=-13\)

   \(x=-\frac{13}{5}\)

4. \(4(x+7)=-3(15-3x)\)

   \(4x+28=-45+9x\)

   \(28+45=9x-4x\)

   \(73=5x\)

   \(x=\frac{73}{5}\)

5. \(1.6x-2.5=0.2+1.98\)

   \(1.6x-2.5=2.18\)

   \(1.6x=4.68\)

   \(x=4.68:1.6=2.925\)

6. \(3.64+4.7x=6.4(0.2x-0.5)\)

   \(3.64+4.7x=1.28x-3.2\)

   \(4.7x-1.28x=-3.2-3.64\)

   \(3.42x=-6.84\)

   \(x=-2\)

7. \(\frac{5}{7}x-\frac{4}{5}=\frac{23}{25}+\frac{3}{14}x\)

   \(\left(\frac{5}{7}-\frac{3}{14}\right)x=\frac{23}{25}+\frac{4}{5}\)

   \(\frac{1}{2}x=\frac{23}{25}+\frac{20}{25}=\frac{43}{25}\)

   \(x=\frac{86}{25}\)

Ответ: 1) \(x=21\); 2) \(x=6\); 3) \(x=-\frac{13}{5}\); 4) \(x=\frac{73}{5}\); 5) \(x=2.925\); 6) \(x=-2\); 7) \(x=\frac{86}{25}\).