16 units. The long side is 7. And the short sides are 1. 7+1=8. Then you would multiply that by 2. Since each value should represent two sides. You get 16 after that
Let 2x – y = 3 ——— equation 1
Let x + 5y = 14 ——— equation 2
Making x the subject in eqn 1, = x = y + 3 / 2 ——— eqn 3
• Put eqn 3 in eqn 2
(y + 3 / 2) + 5y = 14
6y = 14 – 3/2
6y = 25/2
y = 25/12
• put y = 25/12 in eqn 3
x = (25/12 + 3/2)
x = 43/12
<h2>Answer:</h2>
Number of biology textbooks sold: 257 textbooks
Number of psychology textbooks sold: 181 textbooks
<h2>Explanations:</h2>
Let the total number of biology textbook sold be "a"
Let the total number of psychology textbook sold be "b"
If a textbook store sold a combined total of 438 biology and psychology textbooks in a week, then:
a + b = 438 ................... 1
If the number of psychology textbooks sold was 76 less than the number of biology textbooks sold, then;
b = a - 76 ...................... 2
Substitute equation 2 into 1
a + (a-76) = 438
a + a - 76 = 438
2a = 438 + 76
2a = 514
a = 514/2
a = 257 biology textbooks
From equation 2;
b = a - 76
b = 257 - 76
b = 181 psychology textbooks
Number of biology textbooks sold: 257 textbooks
Number of psychology textbooks sold: 181 textbooks
