Dave pays two-fifth of his salary for rent, 16% of the salary for grocery and one-fourth of the salary for travel. He saves the remaining $1,368. How much does he earn?

Can anybody help me?

Let x = the amount he earns.

0.4x + 0.16x + 0.25x + 1368 = x

0.81x + 1,368 = x
1,368 = x - 0.81x
1,368 = 0.19x
1,368/0.19 = x
7,200 = x