The temperatures recorded were -18.072 Celcius and -11.927 Celcius.
Step-by-step explanation:
Step 1; Assume one of the temperatures is given a value of x. One of the measurements that Mark measured was 2/3 of the other. So if one value is x then the other is 2/3x.
Step 2; Now we equate the two temperatures to find their values. it is given their sum is -30 Celcius so the sum of x and 2/3x is -30. The equation is as follows
x + 2/3 x = -30, x + 0.666x = -30, 1.666x = -30, x= -18.072
Step 3; After solving x we have found the value of one of the temperatures. The other can be found by multiplying 2/3 with x i.e. 2/3 * -18.072 which equals -11.927. So temperatures are -18.072 Celcius and -11.927 Celcius.