Greetings from Brasil...
According to the statement of the question, we can assemble the following system of equation
X = 7 + 3Y i
X + Y = 75 ii
So, multiplying ii by -1 and adding with i
X = 7 + 3Y
- X - Y = - 75
- Y = 7 + 3Y - 75
4Y = 68
Y = 17
for X we will use ii:
X + Y = 75
X + 17 = 75
X = 58
The smaller number is: 17
