I Need More Help.how Many Stamps Did Allen Buy?

Perimeter of isosceles triangle = 2a + b
where a = side with similar length
b = base
so here, a = 8 cm less than 4 times the length of the base
a = 4b - 8
put this value of a in the perimeter's equation
Perimeter = 2a + b,

  29 = 2 (4b - 8) + b,

  :29 = 8b - 16 + b,

   :29 +16 = 9b,

   :45 = 9b,

   :b = 5.


   Now the value of a = 4b - 8,

   a = 4(5) - 8,

   a = 20 - 8,

   a = 12.

The key to the stamp question is that the total ends in 6. Only combinations of the 37 cent stamp can result in an answer that ends in 6, so taking the 7 from the 37 cent stamp the first two multiples of seven that end in 6 are 56 and 126
8 x 7 = 56
so 8 stamps @37 c = 296
so with 12 stamps left (allen only bought 20 stamps so 20 - 8 =12)
12 x 20 = 240
240 + 296 = 536 (so this does not work)

18 x 7 = 126
so 18 x 37 c = 666c
so with 2 stamps left
2 x 20 = 40 c
666c + 40 c = 706 cents which = $7.06