Question

3x2=7 5x4=23 7x6=47 9x8=79 10x9=?

Answer 1

`(a* b) = (a* b) +(b -1) = c \\ \\ 3 * 2 = (3* 2) +(2-1) = 6 +1=7 \\ \\ 5 * 4 = (5* 4) +(4-1) = 20 +3=23 \\ \\ 7 * 6 = (7* 6) +(6-1) = 42 +5=47 \\ \\ 9 * 8= (9* 8) +(8-1) = 72 +7=79 \\ \\ \\ \\ 10 * 9 = (10* 9) +(9-1) = 90 +8=\boxed {\bf{98}}\\\sf {10* 9 = \boxed{\bf {98}}}`