After a brand TV set is reduced by M yuan according to the original price, it is reduced by 10%, and the current price is n yuan. How much is the original price of the TV set? Please!

After a brand TV set is reduced by M yuan according to the original price, it is reduced by 10%, and the current price is n yuan. How much is the original price of the TV set? Please!

Let the original price be X
X-m - (x-m) 10% = n multiplied by 100
100X-100M-10x+10m=100n
90x-90m=100n
x=(100n+90m)/90