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This is the fourth time to share this question and no answers Here is it and i found an answer but i can't understand any thing neither the question nor the answer so i need help please and if there is any other solution or way to solve it help please 

 

A sum equals L.E 8,it is wanted to change it to 21 banknotes,some of them are 25 piasters and the others are of 50 piasters .find the number of banknotes of each type.

 

the answer i read 

let the number of banknotes of P.T25 be X and the number of banknotes of P.T50 be Y

X+Y=21 (EQUATION 1)

25X+50Y=800

DIVINDG BY 25

X+2Y=32 (EQUATION 2 )

SUBTRACTING 1 FROM 2 

Y=11,X=10

THE NUMBER OF BANKNOTES OF P.T 25 IS 10 AND THE NUMBER OF BANKNOTES OF P.T 50 IS 11

                        "HELP"

 

Answer 1

L.E. 8 = 800 piasters. 25x + 50y = 800, and x + y = 21.

 

Can you solve the system of equations from there? (Hint, divide that first equation by 25.)