Juan works as a tutor for $7 an hour and as a waiter for $14 an hour. This month, he worked a combined total of 103 hours at his two jobs. Let be the number of hours Juan worked as a tutor this month. Write an expression for the combined total dollar amount he earned this month.

An expression for the combined total dollar amount he earned this month is $(7x + 14y) where x + y = 103.

Explanation:

Let the no. of hours worked as tutor be x

Earning as tutor in 1 hour = $7

Earning as tutor in x hour = $7*x = $7x

Let the no. of hours worked as waiter be y

Earning as waiter in 1 hour = $14

Earning as waiter in y hour = $14*y = $14y

Given that total hours worked in the month = 103 hours

therefore, x + y = 103 > (1)

Total amount earned in the month = Earning as tutor in x hour + Earning as waiter in y hour = $(7x + 14y)

An expression for the combined total dollar amount he earned this month is $(7x + 14y) where x + y = 103.

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explanation:

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.