One number is 4 less than 3 times a second number. If 3 more than two times the first number is decreased by 2 times the second number, the result is 11. Use the substitution method. What is the first number?

1 Answer
Jun 16, 2016

n_1=8
n_2=4

Explanation:

One number is 4 less than -> n_1=?-4
3 times " ........................."->n_1=3?-4
the second number color(brown)(".........."->n_1=3n_2-4)
color(white)(2/2)

If 3 more " ..........................................."-> ?+3
than two times the first number" ............"->2n_1+3
is decreased by "..................................."->2n_1+3-?
2 times the second number" ................."->2n_1+3-2n_2
the result is 11color(brown)(" ....................................."->2n_1+3-2n_2=11)

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color(white)(.)n_1=3n_2-4 .....................Equation (1)
2n_1+3-2n_2=11...........Equation (2)

Substitute for n_1 in equation (2) using equation (1)

color(brown)(2n_1+3-2n_2=11)" "color(blue)( ->2(3n_2-4)+3-2n_2=11)

Multiplying out the brackets

6n_2-8+3-2n_2=11

4n_2-5=11

Add 5 to both sides

4n_2=16

Divide both sides by 4

" "color(green)(n_2=4)
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Substitute n_2=4 into equation (1)

n_1=3(4)-4

n_1=12-4

" "color(green)(n_1=8)
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Check: One number is 4 less than 3 times the second number

8=3(4)-4=8 confirmed!