Four children have small toys. the first child has 1/10 of the toys, the second child has
12 more toys than the first, the third child has one more toy of what the first child has
and the fourth child has double the third child. how many toys are there?

A,b,c,d
x=number of toys total
a+b+c+d=x
a=(1/10)x
b=12+(1/10)x
c=1+(1/10)x
d=2(1+(1/10)x)=2+(2/10)x
add them

(1/10)x+12+(1/10)x+1+(1/10)x+2+(2/10)x=x
group like terms
(1/10)x)+(1/10)x+(1/10)x+(2/10)x+12+1+2=x
add like terms
(5/10)x+15=x
(1/2)x+15=x
subtract (1/2)x from both sides
15=(1/2)x
multily both sides by 2/1 to clear fraction
30=x

30 total toys