Question

Por favor me ajudem e para amanha​

Answer 1

Resposta:

Explicação passo a passo:

$4) \frac{x}{15-x} = \frac{\frac{6}{5} }{3} \\\\\frac{x}{15-x} = \frac{6}{15} \\\\15x=90-6x\\21x=90\\x=\frac{90}{21} = \frac{30}{7} ou 4,2 = \frac{21}{5} \\\\5) \frac{x}{21-x} = \frac{2}{5} \\\\5x=42-2x\\7x=42\\x=\frac{42}{7} = 6\\\\\\21-x=y\\y=21-6\\y= 15\\\\\frac{4}{9} = \frac{x}{52-x} \\9x=-4x+208\\13x=208\\x=\frac{208}{13} = 16\\52-x=y\\y=52-16\\y= 36\\\\6) \frac{x}{x+3+x-x} = \frac{10}{15} \\15x=10x+30\\5x=30\\x = 6$$7) \frac{x-1}{12}=\frac{3}{9} \\ 9x-9=36\\\\9x=45\\x=\frac{45}{9} = 5$