3x-y=25
x+4y=-22
3x-y=25
-3x-12y=66
-13y=91
y=-7
x+4(-7)=-22
x=6
three times a first number decreased by a second number is 25. the first number increased by four times the second number is -22. find the numbers
4 answers
first number -- x
second number ---y
translation:
" three times a first number decreased by a second number is 25" ---> 3x - y = 25
" the first number increased by four times the second number is -22" ---> x + 4y = -22
form 2nd equation: x = -4y - 22
sub into 1st equation:
3(-4y-22) - y = 25
-12y - 66 - y = 25
-13y = 91
y = -7
then x = 28-22 = 6
First number is 6, then second is -7
check:
3(6) - (-7) = 25
6 + 4(-7) = -22 , looks good
second number ---y
translation:
" three times a first number decreased by a second number is 25" ---> 3x - y = 25
" the first number increased by four times the second number is -22" ---> x + 4y = -22
form 2nd equation: x = -4y - 22
sub into 1st equation:
3(-4y-22) - y = 25
-12y - 66 - y = 25
-13y = 91
y = -7
then x = 28-22 = 6
First number is 6, then second is -7
check:
3(6) - (-7) = 25
6 + 4(-7) = -22 , looks good
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