Well, we can input both variables to check and see if the numbers hold.
-691 = -51(-15) - 74
-691 = 765-64
-691 = 701
(-15, -691) does not make the equation true.
Each number is 4 times the previous number"
2*4 = 8
8*4 = 32
32*4 = 128
so next 3 are:
128 * 4 = 512
512*4 = 2048
2048 * 4 = 8192
512 , 2048, 8192
706 ÷ 0363
1.94490358127 is your answer.