On a busy day, a shop sells a total of 15 desks and chairs for a total amount of $960.The desks sell for $120 each and the chairs sell for $50 each. (a) Express the information as two equations. Let d equal the number of desks and let c equal the number of chairs.
(b) Solve the equations simultaneously to find how many of each were sold.

- sold 15 desks + chairs

- each desk is $120

- each chair is $50

- total amount is $960

- desk = d

- chairs = c

(a) i/ d + c = 15

ii/ 120d + 50c = 960

(b) d+c = 15 (1)

120d + 50c = 960 (2)

from (1) d+c = 15

c = 15-d (3)

substitute (3) into (2)

120d + 50c = 960

120d + 50(15-d) = 960

120d + 750 - 50d = 960

120d - 50d = 960 - 750

70d = 210

d = 210/70

d = 3

substitute d=3 into (3)

c = 15-d

c = 15-3

c = 12

thus, 3 desks and 12 chairs were sold