Acollection of dimes and nickels is worth $8.40 there are 106 coins how many of each are there

There are 62 dimes and 44 nickels.

N + D = 106 (There are 106 coins in all.)
1 nickel = 5 cents.
1 dime = 10 cents.
5*N + 10*D = 840 ($8.40 = 840 cents)
N + D = 106 (1)
N = (106 - D)
5*N + 10*D = 840 (2)
5*(106-D) + 10*D = 840
530 - 5*D + 10*D = 840
5*D = 840 - 530
5*D = 310
D = 310/5 = 62
Eq(1) N + D = 106
N + 62 = 106
N = 106 - 62
N = 44

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.