$$\begin{gathered} 37 2 ? 23 2 = 840 \\ Required number = 840 = 28 . 98 \end{gathered}$$

$$\begin{gathered} ( a ? b ) 2 = a 2 + b 2 - 2 ab \\ ? 16 = a 2 + b 2 ? 90 \\ ? a 2 + b 2 = 106 \\ a 3 ? b 3 = ( a ? b ) ( a 2 + b 2 + ab ) \\ ? a 3 ? b 3 = 4 X ( 106 + 45 ) \\ ? a 3 ? b 3 = 4 X 151 \\ ? a 3 ? b 3 = 604 \end{gathered}$$

a/(a + b) = 15/21 ? a = 15, a + b = 21

? b = 21? 15 = 6
? a ? b =15 ? 6 = 9
? (a + b)/(a ? b) = 21/9

? 4(798 X 579) / (798 X 579)
? 4

x : y = 8 : 15
If y = 10, x = 8/15 X 10
y = 16/3