Astamp collector has some 15¢ stamps and some 20¢ stamps. the number of 15¢ stamps is eight less
than three times the number of 20¢ stamps. the total value is $4. find the number of each type of
stamp in the collection.

Step-by-step explanation:

Let variable x represent the 15¢ stamps, and variable y  represent 20¢ stamps.

x= 3y-8

0.15x+0.20y = 4

Replace x in the second equation by (3y-8)

0.15(3y-8) + 0.20y = 4

0.45y - 1.2 +0.20y = 4

Collect like terms;

0.45y+0.20y = 4+1.2

0.65y = 5.2

Divide both sides by 0.65 to solve for y;

y= 5.2/0.65

y = 8

Replace in equation " x=3y-8 " to solve for x;

x = (3*8) -8

x=24 - 8

x = 16

Therefore, the 15¢ stamps are 16 in number, and the 20¢ stamps are 8 in number.

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents