Question

38)Sa se afle a, b si c stiind ca: a+b=34 b+c=31 a+c=39 a+b=41 a+c=31 b+c=51

39)Afla numarul necunoscut din relatiile:
1) (a x 5-4):3 + 8:2=6
2)80 + [(60 : a +9 ) x 6 x 5 ] =380
3)204 + [120 - (30 - 4 x a) x 9 :30] : 123=1

Answer 1

38)
a+b=34
b+c=31
a+c=39
2(a+b+c)=34+31+39
a+b+c=104/2=52
a=52-31=21
b=52-39=13
c=52-34=18

a+b=41
a+c=31
b+c=51
2(a+b+c)=41+31+51
a+b+c=123/2=61,5
a=61,5-51=10,5
b=61,5-31=30,5
c=61,5-41=20,5

39)
1) (a x 5-4):3 + 8:2=6
(5a-4):3=6-4
5a-4=2×3
5a=6+4
a=10:5
a=2

2)80 + [(60 : a +9 ) x 6 x 5 ] =380
(60 : a +9 ) x 30  =380-80
60 : a +9    =300:30
60 : a +9    =10
60 : a    =10-9
60:a=1
a=60

3)204 + [120 - (30 - 4 x a) x 9 :30] : 123=1
 [120 - (30 - 4a) x 9 :30] : 123=1-204
120 - (30 - 4a) x 9 :30=-203×123
 - (30 - 4a) x 9 :30=-24969-120
 - (30 - 4a) x 9 :30=-25089
 (30 - 4a) x 9 =25089×30
30 - 4a =752670:9
 - 4a=83630-30
 - 4a=83600
a=-20900