急急急急急急急急急急....有英文數唔識(10funs)

a)
let A is the total amount of money
A = 2x(5) + x(2)
A = 12x
x = A/12

therefore the total amount of money is $A, then x = A/12

b)
let B is the number of coins
B = 2x + x
B = 3x
x = B/3

therefore the number of coins is B , then x = B/3

2007-08-14 16:38:09 補充：
b) other solutionlet B is the number of coinsB = 2x xB = 3xx = B/3A/12 = B/3B = A/4therefore the number of coins is A/4 , then x = A/12

Mary has 2x five-dollar coins and x two-dollar coins.
By adding one condition,find a possible value of x.
(a) Mary has 2 X $5 + x X $2 = $10 + $2 = $12x
If the total amount of money is $24, then x=2 .
(b)If the number of coins he has = 2x + x = 3x
If the number of coins is 6,then x= 2 .