Option C is correct answer
Sum of temperatures for Monday ($M$), Tuesday ($T$), and Wednesday ($W$)
$M + T + W = 41 \times 3 = 123^\circ\text{C}$. ------> (1)
Sum of temperatures for Tuesday ($T$), Wednesday ($W$), and Thursday ($Th$)
$T + W + Th = 43 \times 3 = 129^\circ\text{C}$. --------> (2)
Now from equation (1) and (2) , we do
$(T + W + Th) - (M + T + W) = 129 - 123$
$Th - M = 6^\circ\text{C}$
it is given that Thursday's temperature is 15% higher than Monday's,
$Th = M + 0.15M = 1.15M$ -----> (3)
$Th - M = 0.15M$
$0.15M = 6$
$M = \frac{6}{0.15} = 40^\circ\text{C}$
From equation (3) Thursday's temperature ($Th$)
$Th = 1.15 \times 40 = 46^\circ\text{C}$
