Question

21. Să se afle x număr natural:
a) 12(x + 1) - 4(x + 1) = 40 b) 7(8-x)+3(8 - x) = 60 c) 15(X-4)-808-4) = 21
d) 13(2x +4)-5(2x + 4) = 48 e) 6(4x --2) +5(4x - 2) = 18+2(4x-2)​

Answer 1

a)

$\\12(x + 1) - 4(x + 1) = 40\\8\left(x+1\right)=40\\x+1=5\\x=5-1\\x=4$

b)

$7(8-x)+3(8 - x) = 60\\10\left(8-x\right)=60\\8-x=6\\-x=-2\\x=2$

c)

$15\left(x-4\right)-808-4=21\\15\left(x-4\right)=833\\\frac{15\left(x-4\right)}{15}=\frac{833}{15}\\x-4=\frac{833}{15}\\x==\frac{4\cdot \:15}{15}+\frac{833}{15}\\x=\frac{893}{15}$

d)

$3(2x +4)-5(2x + 4) = 48\\-2\left(2x+4\right)=48\\2x+4=-24\\2x=-28\\x=-14$

e)

$6(4x --2) +5(4x - 2) = 18+2(4x-2)​\\11\left(4x-2\right)=18+2\left(4x-2\right)\\44x-22=8x+14\\44x=8x+36\\36x=36\\x=1$