Question 158974
She needs 33 cents in postage for each letter, and 20 cents for each postcard. 
She spends $3.58 in postage. How many letters and postcards did she send?
:
Let x = no. of letters
Let y = no. of postcards
:
.33x + .20y = 3.58
;
.2y = 3.58 - .33x
:
y = {{{(3.58-.33x)/.2}}}
y = 17.9 - 1.65x
:
Substitute integers values for x, until you get an integer value for y
:
x = 6 will work
y = 17.9 - 1.65(6)
y = 17.9 - 9.9
y = 8
:
We have 6 letters, 8 post cards
;
:
Check:
 .33(6) + .20(8) =
1.98 + 1.60 = 3.58