Question

△+□=12,△+⊙=14,△=□+⊙+⊙

Answer 1

△=x
□=y
⊙=z
△+□=12
x+y=12 (1)

△+⊙=14
x+z=14 (2)

△=□+⊙+⊙
x=y+2z
x-y-2z=0 (3)

sub (1) and (2) into (3)
x-(12-x)-2(14-x) =0
4x=40
x=10

from (1)
10+y=12
y=2

from (2)
10+z=14
z=4

△=x=10
□=y=12
⊙=z=14

Answer 2

∵△＋□＝12∴△＝12－□
又∵△＋⊙＝14∴△＝14－⊙
□＋⊙＋⊙＝12－□ □＋⊙＋⊙＝14－⊙
2□＝12－2⊙ □＋3⊙＝14
□＝6－⊙ □＝14－3⊙
6－⊙＝14－3⊙
2⊙＝14－6
⊙＝4
□＝6－4＝2
△＝2＋4＋4＝10

Answer 3

△=10
□=2
⊙=4