7. Lee has $10.20 in a jar that contains only nickels
and dimes. There are 140 coins in the jar. How
many nickels are in Joseph's jar?
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Solution:

Let "d" be the number of dimes

Let "n" be the number of quarters

1 dime = $ 0.10

1 nickel = $ 0.05

There are 140 coins in the jar

Therefore,

d + n = 140

n = 140 - d ------- eqn 1

Lee has $10.20 in a jar that contains only nickels  and dimes

Therefore,

0.1d + 0.05n = 10.20 -------- eqn 2

Substitute eqn 1 in eqn 2

0.1d + 0.05( 140 - d) = 10.20

0.1d + 7 - 0.05d = 10.20

0.05d = 3.2

Divide both sides by 0.05

d = 64

Substitute d = 64 in eqn 1

n = 140 - 64

n = 76

Thus there are 76 nickels in jar

step-by-step explanation:

total income = price of one ticket   *   number of tickets sold

  y                 =     4                                   x

so the equation is y=4x     with x≥0   because number of tickets sold can not be negative

thus the equation is a semi -line with an end point at

(0,0)

passing through :

x=1     y=4(1) = 4   so through (1,4)

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step-by-step explanation: