10)Aducem termenii din paranteza la acelasi numitor :36
[tex]( \frac{5*3}{12*3} + \frac{7*2}{18*2} ): \frac{29}{100} = \frac{15+14}{36} * \frac{100}{29} - \frac{7}{9} =[/tex]
[tex] \frac{29}{36}* \frac{100}{29} - \frac{7}{9} =
simplificam 29 cu 29 prin 29 si 36 cu 100 prin 4 si obtinem
[/tex][tex] \frac{1}{9} * \frac{25}{1} - \frac{7}{9} =[/tex]
[tex] \frac{25}{9} - \frac{7}{9} =[/tex]
[tex] \frac{18}{9} =2[/tex]
11)7a2b div cu 45⇒ 7a2b div cu 5 ⇒b∈{0,5}
7a2b div cu 9 ⇒(7+a+2+b) div cu 9
pt b=0⇒7a20 div cu 9⇒a=9⇒7920
b=5⇒7a25 div cu 9⇒a=4⇒7425
12)x+y+z=20
[tex] \frac{x}{2} = \frac{y}{3} = \frac{z}{5}= \frac{x+y+z}{2+3+5} = \frac{20}{10}=2 [/tex]
[tex] \frac{x}{2}=2 [/tex]⇒x=2*2⇒x=4
[tex] \frac{y}{3} =2[/tex]⇒y=2*3⇒y=6
[tex] \frac{z}{5}=2 [/tex]⇒z=2*5⇒z=10
