Question

determine o valor de x nas seguintes proporções

a) x+3 3
••••••• = ••••••
x-1 18


b) x-1 x
••••••• = •••••
18 36


c) x-10 3
•••••••• = ••••••
15 5


d) x+5 16
••••••• = •••••••
x 20
​

Answer 1

$a) \frac{x + 3}{x - 1} = \frac{3}{18} \\ \\ 18(x + 3) = 3(x - 1) \\ \\ 18x + 54 = 3x - 3 \\ \\ 18x - 3x = - 3 - 54 \\ \\ 15x = - 57 \\ \\ x = \frac{ - 57}{15} \\ \\ x = - \frac{19}{5}$

$\frac{x - 1}{18} = \frac{x}{36} \\ \\ 18x = 36x - 36 \\ \\ 18x - 36x = - 36 \\ \\ - 18x = - 36 \\ \\ x = \frac{36}{18} \\ \\ x = 2$

$\frac{x - 10}{15} = \frac{3}{5} \\ \\ 5x - 50 = 45 \\ \\ 5x = 45 + 50 \\ \\ 5x = 95 \\ \\ x = \frac{95}{5} \\ \\ x = 19$

$\frac{x + 5}{x} = \frac{16}{20} \\ \\ 20x + 100 = 16x \\ \\ 20x - 16x = - 100 \\ \\ 4x = - 100 \\ \\ x = - \frac{100}{4} \\ \\ x = 25$