Answer:176 psychology textbooks and 98 Biology textbooks were sold.
Step-by-step explanation:
Let x represent the number of psychology textbooks that were sold.
Let y represent the number of biology textbooks that were sold.
textbook store sold a combined total of 274 psychology and biology textbooks in a week. This means that
x + y = 274 - - - - - - - - - - -1
The number of psychology textbooks sold was 78 more than the number of biology textbooks sold. This means that
x = y + 78
Substituting x = y + 78 into equation 1, it becomes
y + 78 + y = 274
2y = 274 - 78
2y = 196
y = 98
x = y + 78 = 98 + 78
x = 176
Answer:psychology books sold=173
Biology books sold=95
Step-by-step explanation:
Psychology textbooks sold=p
Biology textbooks sold=b
P+b=274
P-78=b
P+P-78=274
2P-78=274
2P=274+78
2P=352
P=352/2
P=173
Substance P=173 in P-78=b
173-78=b
95=b b=95
