She saved 40% of monthly wage in month one (spent 60%)

She saved 25% of monthly wage in month two (spent 75% i.e. 60% x 1.2525% more)

So saved a total of 65% of a monthly wage

Total savings=$2600.00

monthly wage x 0.65 = $2600

so, monthly wage = $2600/0.65 = $4000