I thought those were berries, but I went this way...
OK ... the child in the last picture is holding two containers of berries, and there's a change of sign... yikes...
So first the shoes...
6x=30
x=5
And then...
Then the boy ... making him y
2y + 2x =20
2y + 2(5)=20
2y+ 10 =20
2y=10
y=5
And then the berries/ice cream... z
2z +2z +y =13
4z + y =13
4z + 5 =13
4z=8
z=2
So then... if we presume the boy holding the berries is addition...
z(x + y + z + z)=?
2(5+5+2+2)=?
2(14)=?
28=28
We can complicate things a bit more. The object the child is holding is tilted one to the right and one to the left, so we can conclude that one is positive and the other is negative, haha.
10 + (x + 4 - 4) * 4 = y
10 + (x + 0) * 4 = y
10 + (x) * 4 = y
10 + 4x = y
y = 4x + 10
I'm out here digging back into middle school math ... my brain was like, "Wait, what?" as it was ... so I didn't even think about positive and negative...