№5. При каких значениях х равенство будет верным? 1) х/3 = 5/15; 2) 4/x = 12/30; 3) 7/8 = x/40; 4) 6/19 = 24/x.

1) \[\frac{x}{3} = \frac{5}{15}\] \[ x = \frac{5 \cdot 3}{15}\] \[ x = \frac{15}{15}\] \[ x = 1\] 2) \[ \frac{4}{x} = \frac{12}{30}\] \[ x = \frac{4 \cdot 30}{12}\] \[ x = \frac{120}{12}\] \[ x = 10\] 3) \[ \frac{7}{8} = \frac{x}{40}\] \[ x = \frac{7 \cdot 40}{8}\] \[ x = \frac{280}{8}\] \[ x = 35\] 4) \[ \frac{6}{19} = \frac{24}{x}\] \[ x = \frac{24 \cdot 19}{6}\] \[ x = \frac{456}{6}\] \[ x = 76\]