Penjualan seratus delapan puluh rupiah. Rugi 10 persen berap pembelianya

Jual =Rp.180
rugi = 10% = 10%*180 = Rp.18

Beli =Jual- rugi = 180 -18 =Rp.162

penjualan (p) = Rp 180,00
rugi = 10 %
pembelian (b) = ...???

rugi = b - p

.................b - p
% rugi = -------- × 100%
....................b

..............b - 180
10 % = ----------- × 100 %
.................b

.............100b - 18.000
10 % = ---------------------
...................100b

10/100 × 100b = 100b - 18.000
10b = 100b - 18.000
100b - 10b = 18.000
90b = 18.000
b = 18.000/90
b = Rp 200,00


Jadi pembeliannya adalah Rp 200,00