(0.85 % of 405 ) + (2.25 % of 550 )=?

The value of x for which the expressions 7x + 13 and 13x - 7 become equal is _____ .

? – 2³ =(7² – 12 ) + ( 10² -17)

115% of 4880 – 85% of 1640 = ?

12 × 15 + 27 – ? = 28% of 400