Ihave 31 stamps in total. i have 4 more 1 cent stamps than 8 cent stamps and twice as many one cent stamps as 12 cent stamps. if my stamps are worth $1.78 altogether how many one cent stamps do i have?

There area 14 one cent stamps

Step-by-step explanation:

Let

x > the number of 1 cent stamps

y > the number of 8 cent stamps

z > the number of 12 cent stamps

we know that

0.01x+0.08y+0.12z=1.78 > equation A

x=y+4 > y=x-4 > equation B

x=2z > z=0.5x > equation C

substitute equation B and equation C in equation A and solve for x

0.01x+0.08(x-4)+0.12(0.5x)=1.78

0.01x+0.08x-0.32+0.06x=1.78

0.15x=1.78 +0.32

0.15x=2.10

x=14

therefore

There area 14 one cent stamps