30 Решите уравнение: a) 245 ⋅ (m - 33) = 4410; б) 864k - 470k = 5910; в) (3x +12) : 72 = 21; г) 420 : (у – 15) = 84.

Решаем уравнения:

a) $$245 \cdot (m - 33) = 4410$$

$$m - 33 = \frac{4410}{245}$$

$$m - 33 = 18$$

$$m = 18 + 33$$

$$m = 51$$

б) $$864k - 470k = 5910$$

$$394k = 5910$$

$$k = \frac{5910}{394}$$

$$k = 15$$

в) $$(3x + 12) : 72 = 21$$

$$3x + 12 = 21 \cdot 72$$

$$3x + 12 = 1512$$

$$3x = 1512 - 12$$

$$3x = 1500$$

$$x = \frac{1500}{3}$$

$$x = 500$$

г) $$420 : (y - 15) = 84$$

$$y - 15 = \frac{420}{84}$$

$$y - 15 = 5$$

$$y = 5 + 15$$

$$y = 20$$

Ответ: a) m = 51; б) k = 15; в) x = 500; г) y = 20.