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