1) 10+10+10 = 30

2) 5 +5+10=20

3) 4+4+5=13

4) 5+5*2 = 15,

Lets say, a shoe as x, boy as y, and a snack packet as z,

So the equation are,

1) 2x+2x+2x=30

x = 30/(2+2+2)

x = 5;

2) y + y +2x =20;

2y+2(5)=20;

y = 5;

3) 2z + 2z + y = 13;

4z + 5 = 13

z = (13-5)/4

z = 2;

So for the last equtation

x + y * z =?

5+5*2 = 15 //using the math operations precedence, Multiplication executes first.